ZCML directives — zope.configuration 4.0 documentation

### Navigation

- index
- modules |
- next |
- previous |
- zope.configuration 4.0 documentation »

# ZCML directives

Components may be registered using the registration API exposed by `zope.component` (provideAdapter, provideUtility, etc.). They may also be registered using configuration files. The common way to do that is by using ZCML (Zope Configuration Markup Language), an XML spelling of component registration.

In ZCML, each XML element is a directive. There are different top-level directives that let us register components. We will introduce them one by one here.

This helper will let us easily execute ZCML snippets:

    >>> from cStringIO import StringIO
    >>> from zope.configuration.xmlconfig import xmlconfig
    >>> def runSnippet(snippet):
    ...     template = """\
    ...     <configure xmlns='http://namespaces.zope.org/zope'
    ...                i18n_domain="zope">
    ...     %s
    ...     </configure>"""
    ...     xmlconfig(StringIO(template % snippet))

## adapter

Adapters play a key role in the Component Architecture. In ZCML, they are registered with the <adapter /> directive.

    >>> from zope.component.testfiles.adapter import A1, A2, A3, Handler
    >>> from zope.component.testfiles.adapter import I1, I2, I3, IS
    >>> from zope.component.testfiles.components import IContent, Content, Comp, comp

Before we register the first test adapter, we can verify that adapter lookup doesn’t work yet:

    >>> from zope.component.tests.examples import clearZCML
    >>> clearZCML()
    >>> from zope.component.testfiles.components import IApp
    >>> IApp(Content(), None) is None
    True

Then we register the adapter and see that the lookup works:

    >>> runSnippet('''
    ...   <adapter
    ...       factory="zope.component.testfiles.components.Comp"
    ...       provides="zope.component.testfiles.components.IApp"
    ...       for="zope.component.testfiles.components.IContent"
    ...       />''')

    >>> IApp(Content()).__class__
    <class 'zope.component.testfiles.components.Comp'>

It is also possible to give adapters names. Then the combination of required interface, provided interface and name makes the adapter lookup unique. The name is supplied using the `name` argument to the <adapter /> directive:

    >>> from zope.component.tests.examples import clearZCML
    >>> clearZCML()
    >>> import zope.component
    >>> zope.component.queryAdapter(Content(), IApp, 'test') is None
    True

    >>> runSnippet('''
    ...   <adapter
    ...       factory="zope.component.testfiles.components.Comp"
    ...       provides="zope.component.testfiles.components.IApp"
    ...       for="zope.component.testfiles.components.IContent"
    ...       name="test"
    ...       />''')

    >>> zope.component.getAdapter(Content(), IApp, 'test').__class__
    <class 'zope.component.testfiles.components.Comp'>

### Adapter factories

It is possible to supply more than one adapter factory. In this case, during adapter lookup each factory will be called and the return value will be given to the next factory. The return value of the last factory is returned as the result of the adapter lookup. For examle:

    >>> clearZCML()
    >>> runSnippet('''
    ...   <adapter
    ...       factory="zope.component.testfiles.adapter.A1
    ...                zope.component.testfiles.adapter.A2
    ...                zope.component.testfiles.adapter.A3"
    ...       provides="zope.component.testfiles.components.IApp"
    ...       for="zope.component.testfiles.components.IContent"
    ...       />''')

The resulting adapter is an A3, around an A2, around an A1, around the adapted object:

    >>> content = Content()
    >>> a3 = IApp(content)
    >>> a3.__class__ is A3
    True

    >>> a2 = a3.context[0]
    >>> a2.__class__ is A2
    True

    >>> a1 = a2.context[0]
    >>> a1.__class__ is A1
    True

    >>> a1.context[0] is content
    True

Of course, if no factory is provided at all, we will get an error:

    >>> runSnippet('''
    ...   <adapter
    ...       factory=""
    ...       provides="zope.component.testfiles.components.IApp"
    ...       for="zope.component.testfiles.components.IContent"
    ...       />''')
    Traceback (most recent call last):
       ...
    ZopeXMLConfigurationError: File "<string>", line 4.2-8.8
          ValueError: No factory specified

### Declaring `for` and `provides` in Python

The <adapter /> directive can figure out from the in-line Python declaration (using `zope.component.adapts()` or `zope.component.adapter()` as well as `zope.interface.implements`) what the adapter should be registered for and what it provides:

    >>> clearZCML()
    >>> IApp(Content(), None) is None
    True

    >>> runSnippet('''
    ...   <adapter factory="zope.component.testfiles.components.Comp" />''')

    >>> IApp(Content()).__class__
    <class 'zope.component.testfiles.components.Comp'>

Of course, if the adapter has no `implements()` declaration, ZCML can’t figure out what it provides:

    >>> runSnippet('''
    ...   <adapter
    ...       factory="zope.component.testfiles.adapter.A4"
    ...       for="zope.component.testfiles.components.IContent"
    ...       />''')
    Traceback (most recent call last):
       ...
    ZopeXMLConfigurationError: File "<string>", line 4.2-7.8
          TypeError: Missing 'provides' attribute

On the other hand, if the factory implements more than one interface, ZCML can’t figure out what it should provide either:

    >>> runSnippet('''
    ...   <adapter
    ...       factory="zope.component.testfiles.adapter.A5"
    ...       for="zope.component.testfiles.components.IContent"
    ...       />''')
    Traceback (most recent call last):
       ...
    ZopeXMLConfigurationError: File "<string>", line 4.2-7.8
          TypeError: Missing 'provides' attribute

A not so common edge case is registering adapters directly for classes, not for interfaces. For example:

    >>> clearZCML()
    >>> runSnippet('''
    ...   <adapter
    ...       for="zope.component.testfiles.components.Content"
    ...       provides="zope.component.testfiles.adapter.I1"
    ...       factory="zope.component.testfiles.adapter.A1"
    ...       />''')

    >>> content = Content()
    >>> a1 = zope.component.getAdapter(content, I1, '')
    >>> isinstance(a1, A1)
    True

This time, any object providing `IContent` won’t work if it’s not an instance of the `Content` class:

    >>> import zope.interface
    >>> class MyContent:
    ...     zope.interface.implements(IContent)
    >>> zope.component.getAdapter(MyContent(), I1, '')
    Traceback (most recent call last):
       ...
    ComponentLookupError: ...

### Multi-adapters

Conventional adapters adapt one object to provide another interface. Multi-adapters adapt several objects at once:

    >>> clearZCML()
    >>> runSnippet('''
    ...   <adapter
    ...       for="zope.component.testfiles.components.IContent
    ...            zope.component.testfiles.adapter.I1
    ...            zope.component.testfiles.adapter.I2"
    ...       provides="zope.component.testfiles.adapter.I3"
    ...       factory="zope.component.testfiles.adapter.A3"
    ...       />''')

    >>> content = Content()
    >>> a1 = A1()
    >>> a2 = A2()
    >>> a3 = zope.component.queryMultiAdapter((content, a1, a2), I3)
    >>> a3.__class__ is A3
    True
    >>> a3.context == (content, a1, a2)
    True

You can even adapt an empty list of objects (we call this a null-adapter):

    >>> clearZCML()
    >>> runSnippet('''
    ...   <adapter
    ...       for=""
    ...       provides="zope.component.testfiles.adapter.I3"
    ...       factory="zope.component.testfiles.adapter.A3"
    ...       />''')

    >>> a3 = zope.component.queryMultiAdapter((), I3)
    >>> a3.__class__ is A3
    True
    >>> a3.context == ()
    True

Even with multi-adapters, ZCML can figure out the `for` and `provides` parameters from the Python declarations:

    >>> clearZCML()
    >>> runSnippet('''
    ...   <adapter factory="zope.component.testfiles.adapter.A3" />''')

    >>> a3 = zope.component.queryMultiAdapter((content, a1, a2), I3)
    >>> a3.__class__ is A3
    True
    >>> a3.context == (content, a1, a2)
    True

Chained factories are not supported for multi-adapters, though:

    >>> clearZCML()
    >>> runSnippet('''
    ...   <adapter
    ...       for="zope.component.testfiles.components.IContent
    ...            zope.component.testfiles.adapter.I1
    ...            zope.component.testfiles.adapter.I2"
    ...       provides="zope.component.testfiles.components.IApp"
    ...       factory="zope.component.testfiles.adapter.A1
    ...                zope.component.testfiles.adapter.A2"
    ...       />''')
    Traceback (most recent call last):
       ...
    ZopeXMLConfigurationError: File "<string>", line 4.2-11.8
          ValueError: Can't use multiple factories and multiple for

And neither for null-adapters:

    >>> clearZCML()
    >>> runSnippet('''
    ...   <adapter
    ...       for=""
    ...       provides="zope.component.testfiles.components.IApp"
    ...       factory="zope.component.testfiles.adapter.A1
    ...                zope.component.testfiles.adapter.A2"
    ...       />''')
    Traceback (most recent call last):
       ...
    ZopeXMLConfigurationError: File "<string>", line 4.2-9.8
          ValueError: Can't use multiple factories and multiple for

### Protected adapters

Adapters can be protected with a permission. First we have to define a permission for which we’ll have to register the <permission /> directive:

    >>> clearZCML()
    >>> IApp(Content(), None) is None
    True

    >>> import zope.security
    >>> from zope.configuration.xmlconfig import XMLConfig
    >>> XMLConfig('meta.zcml', zope.security)()
    >>> runSnippet('''
    ...   <permission
    ...       id="y.x"
    ...       title="XY"
    ...       description="Allow XY."
    ...       />
    ...   <adapter
    ...       factory="zope.component.testfiles.components.Comp"
    ...       provides="zope.component.testfiles.components.IApp"
    ...       for="zope.component.testfiles.components.IContent"
    ...       permission="y.x"
    ...       />''')

We see that the adapter is a location proxy now so that the appropriate permissions can be found from the context:

    >>> IApp(Content()).__class__
    <class 'zope.component.testfiles.components.Comp'>
    >>> type(IApp(Content()))
    <class 'zope.location.location.LocationProxy'>

We can also go about it a different way. Let’s make a public adapter and wrap the adapter in a security proxy. That often happens when an adapter is turned over to untrusted code:

    >>> clearZCML()
    >>> IApp(Content(), None) is None
    True

    >>> runSnippet('''
    ...   <adapter
    ...       factory="zope.component.testfiles.components.Comp"
    ...       provides="zope.component.testfiles.components.IApp"
    ...       for="zope.component.testfiles.components.IContent"
    ...       permission="zope.Public"
    ...       />''')

    >>> from zope.security.checker import ProxyFactory
    >>> adapter = ProxyFactory(IApp(Content()))
    >>> from zope.security.proxy import getTestProxyItems
    >>> items = [item[0] for item in getTestProxyItems(adapter)]
    >>> items
    ['a', 'f']

    >>> from zope.security.proxy import removeSecurityProxy
    >>> removeSecurityProxy(adapter).__class__ is Comp
    True

Of course, this still works when we let the ZCML directive handler figure out `for` and `provides` from the Python declarations:

    >>> clearZCML()
    >>> runSnippet('''
    ...   <adapter
    ...       factory="zope.component.testfiles.components.Comp"
    ...       permission="zope.Public"
    ...       />''')

    >>> adapter = ProxyFactory(IApp(Content()))
    >>> [item[0] for item in getTestProxyItems(adapter)]
    ['a', 'f']
    >>> removeSecurityProxy(adapter).__class__ is Comp
    True

It also works with multi adapters:

    >>> clearZCML()
    >>> runSnippet('''
    ...   <adapter
    ...       factory="zope.component.testfiles.adapter.A3"
    ...       provides="zope.component.testfiles.adapter.I3"
    ...       for="zope.component.testfiles.components.IContent
    ...            zope.component.testfiles.adapter.I1
    ...            zope.component.testfiles.adapter.I2"
    ...       permission="zope.Public"
    ...       />''')

    >>> content = Content()
    >>> a1 = A1()
    >>> a2 = A2()
    >>> a3 = ProxyFactory(zope.component.queryMultiAdapter((content, a1, a2), I3))
    >>> a3.__class__ == A3
    True
    >>> [item[0] for item in getTestProxyItems(a3)]
    ['f1', 'f2', 'f3']

It’s probably not worth mentioning, but when we try to protect an adapter with a permission that doesn’t exist, we’ll obviously get an error:

    >>> clearZCML()
    >>> runSnippet('''
    ...   <adapter
    ...       factory="zope.component.testfiles.components.Comp"
    ...       provides="zope.component.testfiles.components.IApp"
    ...       for="zope.component.testfiles.components.IContent"
    ...       permission="zope.UndefinedPermission"
    ...       />''')
    Traceback (most recent call last):
       ...
    ConfigurationExecutionError: exceptions.ValueError: ('Undefined permission id', 'zope.UndefinedPermission')
       in:
       File "<string>", line 4.2-9.8
       Could not read source.

### Trusted adapters

Trusted adapters are adapters that are trusted to do anything with the objects they are given so that these objects are not security-proxied. They are registered using the `trusted` argument to the <adapter /> directive:

    >>> clearZCML()
    >>> runSnippet('''
    ...   <adapter
    ...       for="zope.component.testfiles.components.IContent"
    ...       provides="zope.component.testfiles.adapter.I1"
    ...       factory="zope.component.testfiles.adapter.A1"
    ...       trusted="yes"
    ...       />''')

With an unproxied object, it’s business as usual:

    >>> ob = Content()
    >>> type(I1(ob)) is A1
    True

With a security-proxied object, however, we get a security-proxied adapter:

    >>> p = ProxyFactory(ob)
    >>> a = I1(p)
    >>> type(a)
    <type 'zope.security._proxy._Proxy'>

While the adapter is security-proxied, the object it adapts is now proxy-free. The adapter has umlimited access to it:

    >>> a = removeSecurityProxy(a)
    >>> type(a) is A1
    True
    >>> a.context[0] is ob
    True

We can also protect the trusted adapter with a permission:

    >>> clearZCML()
    >>> XMLConfig('meta.zcml', zope.security)()
    >>> runSnippet('''
    ...   <permission
    ...       id="y.x"
    ...       title="XY"
    ...       description="Allow XY."
    ...       />
    ...   <adapter
    ...       for="zope.component.testfiles.components.IContent"
    ...       provides="zope.component.testfiles.adapter.I1"
    ...       factory="zope.component.testfiles.adapter.A1"
    ...       permission="y.x"
    ...       trusted="yes"
    ...       />''')

Again, with an unproxied object, it’s business as usual:

    >>> ob = Content()
    >>> type(I1(ob)) is A1
    True

With a security-proxied object, we again get a security-proxied adapter:

    >>> p = ProxyFactory(ob)
    >>> a = I1(p)
    >>> type(a)
    <type 'zope.security._proxy._Proxy'>

Since we protected the adapter with a permission, we now encounter a location proxy behind the security proxy:

    >>> a = removeSecurityProxy(a)
    >>> type(a)
    <class 'zope.location.location.LocationProxy'>
    >>> a.context[0] is ob
    True

There’s one exception to all of this: When you use the public permission (`zope.Public`), there will be no location proxy:

    >>> clearZCML()
    >>> runSnippet('''
    ...   <adapter
    ...       for="zope.component.testfiles.components.IContent"
    ...       provides="zope.component.testfiles.adapter.I1"
    ...       factory="zope.component.testfiles.adapter.A1"
    ...       permission="zope.Public"
    ...       trusted="yes"
    ...       />''')

    >>> ob = Content()
    >>> p = ProxyFactory(ob)
    >>> a = I1(p)
    >>> type(a)
    <type 'zope.security._proxy._Proxy'>

    >>> a = removeSecurityProxy(a)
    >>> type(a) is A1
    True

We can also explicitply pass the `locate` argument to make sure we get location proxies:

    >>> clearZCML()
    >>> runSnippet('''
    ...   <adapter
    ...       for="zope.component.testfiles.components.IContent"
    ...       provides="zope.component.testfiles.adapter.I1"
    ...       factory="zope.component.testfiles.adapter.A1"
    ...       trusted="yes"
    ...       locate="yes"
    ...       />''')

    >>> ob = Content()
    >>> p = ProxyFactory(ob)
    >>> a = I1(p)
    >>> type(a)
    <type 'zope.security._proxy._Proxy'>

    >>> a = removeSecurityProxy(a)
    >>> type(a)
    <class 'zope.location.location.LocationProxy'>

## subscriber

With the <subscriber /> directive you can register subscription adapters or event subscribers with the adapter registry. Consider this very typical example of a <subscriber /> directive:

    >>> clearZCML()
    >>> runSnippet('''
    ...   <subscriber
    ...       provides="zope.component.testfiles.adapter.IS"
    ...       factory="zope.component.testfiles.adapter.A3"
    ...       for="zope.component.testfiles.components.IContent
    ...            zope.component.testfiles.adapter.I1"
    ...       />''')

    >>> content = Content()
    >>> a1 = A1()

    >>> subscribers = zope.component.subscribers((content, a1), IS)
    >>> a3 = subscribers[0]
    >>> a3.__class__ is A3
    True
    >>> a3.context == (content, a1)
    True

Note how ZCML provides some additional information when registering components, such as the ZCML filename and line numbers:

    >>> sm = zope.component.getSiteManager()
    >>> doc = [reg.info for reg in sm.registeredSubscriptionAdapters()
    ...        if reg.provided is IS][0]
    >>> print doc
    File "<string>", line 4.2-9.8
      Could not read source.

The “fun” behind subscription adapters/subscribers is that when several ones are declared for the same for/provides, they are all found. With regular adapters, the most specific one (and in doubt the one registered last) wins. Consider these two subscribers:

    >>> clearZCML()
    >>> runSnippet('''
    ...   <subscriber
    ...       provides="zope.component.testfiles.adapter.IS"
    ...       factory="zope.component.testfiles.adapter.A3"
    ...       for="zope.component.testfiles.components.IContent
    ...            zope.component.testfiles.adapter.I1"
    ...       />
    ...   <subscriber
    ...       provides="zope.component.testfiles.adapter.IS"
    ...       factory="zope.component.testfiles.adapter.A2"
    ...       for="zope.component.testfiles.components.IContent
    ...            zope.component.testfiles.adapter.I1"
    ...       />''')

    >>> subscribers = zope.component.subscribers((content, a1), IS)
    >>> len(subscribers)
    2
    >>> sorted([a.__class__.__name__ for a in subscribers])
    ['A2', 'A3']

### Declaring `for` and `provides` in Python

Like the <adapter /> directive, the <subscriber /> directive can figure out from the in-line Python declaration (using `zope.component.adapts()` or `zope.component.adapter()`) what the subscriber should be registered for:

    >>> clearZCML()
    >>> runSnippet('''
    ...   <subscriber
    ...       provides="zope.component.testfiles.adapter.IS"
    ...       factory="zope.component.testfiles.adapter.A3"
    ...       />''')

    >>> content = Content()
    >>> a2 = A2()
    >>> subscribers = zope.component.subscribers((content, a1, a2), IS)

    >>> a3 = subscribers[0]
    >>> a3.__class__ is A3
    True
    >>> a3.context == (content, a1, a2)
    True

In the same way the directive can figure out what a subscriber provides:

    >>> clearZCML()
    >>> runSnippet('''
    ...   <subscriber handler="zope.component.testfiles.adapter.A3" />''')

    >>> sm = zope.component.getSiteManager()
    >>> a3 = sm.adapters.subscriptions((IContent, I1, I2), None)[0]
    >>> a3 is A3
    True

A not so common edge case is declaring subscribers directly for classes, not for interfaces. For example:

    >>> clearZCML()
    >>> runSnippet('''
    ...   <subscriber
    ...       for="zope.component.testfiles.components.Content"
    ...       provides="zope.component.testfiles.adapter.I1"
    ...       factory="zope.component.testfiles.adapter.A1"
    ...       />''')

    >>> subs = list(zope.component.subscribers((Content(),), I1))
    >>> isinstance(subs[0], A1)
    True

This time, any object providing `IContent` won’t work if it’s not an instance of the `Content` class:

    >>> list(zope.component.subscribers((MyContent(),), I1))
    []

### Protected subscribers

Subscribers can also be protected with a permission. First we have to define a permission for which we’ll have to register the <permission /> directive:

    >>> clearZCML()
    >>> XMLConfig('meta.zcml', zope.security)()
    >>> runSnippet('''
    ...   <permission
    ...       id="y.x"
    ...       title="XY"
    ...       description="Allow XY."
    ...       />
    ...   <subscriber
    ...       provides="zope.component.testfiles.adapter.IS"
    ...       factory="zope.component.testfiles.adapter.A3"
    ...       for="zope.component.testfiles.components.IContent
    ...            zope.component.testfiles.adapter.I1"
    ...       permission="y.x"
    ...       />''')

    >>> subscribers = zope.component.subscribers((content, a1), IS)
    >>> a3 = subscribers[0]
    >>> a3.__class__ is A3
    True
    >>> type(a3)
    <class 'zope.location.location.LocationProxy'>
    >>> a3.context == (content, a1)
    True

### Trusted subscribers

Like trusted adapters, trusted subscribers are subscribers that are trusted to do anything with the objects they are given so that these objects are not security-proxied. In analogy to the <adapter /> directive, they are registered using the `trusted` argument to the <subscriber /> directive:

    >>> clearZCML()
    >>> runSnippet('''
    ...   <subscriber
    ...       provides="zope.component.testfiles.adapter.IS"
    ...       factory="zope.component.testfiles.adapter.A3"
    ...       for="zope.component.testfiles.components.IContent
    ...            zope.component.testfiles.adapter.I1"
    ...       trusted="yes"
    ...       />''')

With an unproxied object, it’s business as usual:

    >>> subscribers = zope.component.subscribers((content, a1), IS)
    >>> a3 = subscribers[0]
    >>> a3.__class__ is A3
    True
    >>> a3.context == (content, a1)
    True
    >>> type(a3) is A3
    True

Now with a proxied object. We will see that the subscriber has unproxied access to it, but the subscriber itself is proxied:

    >>> p = ProxyFactory(content)
    >>> a3 = zope.component.subscribers((p, a1), IS)[0]
    >>> type(a3)
    <type 'zope.security._proxy._Proxy'>

There’s no location proxy behind the security proxy:

    >>> removeSecurityProxy(a3).context[0] is content
    True
    >>> type(removeSecurityProxy(a3)) is A3
    True

If you want the trusted subscriber to be located, you’ll also have to use the `locate` argument:

    >>> clearZCML()
    >>> runSnippet('''
    ...   <subscriber
    ...       provides="zope.component.testfiles.adapter.IS"
    ...       factory="zope.component.testfiles.adapter.A3"
    ...       for="zope.component.testfiles.components.IContent
    ...            zope.component.testfiles.adapter.I1"
    ...       trusted="yes"
    ...       locate="yes"
    ...       />''')

Again, it’s business as usual with an unproxied object:

    >>> subscribers = zope.component.subscribers((content, a1), IS)
    >>> a3 = subscribers[0]
    >>> a3.__class__ is A3
    True
    >>> a3.context == (content, a1)
    True
    >>> type(a3) is A3
    True

With a proxied object, we again get a security-proxied subscriber:

    >>> p = ProxyFactory(content)
    >>> a3 = zope.component.subscribers((p, a1), IS)[0]

    >>> type(a3)
    <type 'zope.security._proxy._Proxy'>

    >>> removeSecurityProxy(a3).context[0] is content
    True

However, thanks to the `locate` argument, we now have a location proxy behind the security proxy:

    >>> type(removeSecurityProxy(a3))
    <class 'zope.location.location.LocationProxy'>

### Event subscriber (handlers)

Sometimes, subscribers don’t need to be adapters that actually provide anything. It’s enough that a callable is called for a certain event.

    >>> clearZCML()
    >>> runSnippet('''
    ...   <subscriber
    ...       for="zope.component.testfiles.components.IContent
    ...            zope.component.testfiles.adapter.I1"
    ...       handler="zope.component.testfiles.adapter.Handler"
    ...       />''')

In this case, simply getting the subscribers is enough to invoke them:

    >>> list(zope.component.subscribers((content, a1), None))
    []
    >>> content.args == ((a1,),)
    True

## utility

Apart from adapters (and subscription adapters), the Component Architecture knows a second kind of component: utilities. They are registered using the <utility /> directive.

Before we register the first test utility, we can verify that utility lookup doesn’t work yet:

    >>> clearZCML()
    >>> zope.component.queryUtility(IApp) is None
    True

Then we register the utility:

    >>> runSnippet('''
    ...   <utility
    ...       component="zope.component.testfiles.components.comp"
    ...       provides="zope.component.testfiles.components.IApp"
    ...       />''')
    >>> zope.component.getUtility(IApp) is comp
    True

Like adapters, utilities can also have names. There can be more than one utility registered for a certain interface, as long as they each have a different name.

First, we make sure that there’s no utility yet:

    >>> clearZCML()
    >>> zope.component.queryUtility(IApp, 'test') is None
    True

Then we register it:

    >>> runSnippet('''
    ...   <utility
    ...       component="zope.component.testfiles.components.comp"
    ...       provides="zope.component.testfiles.components.IApp"
    ...       name="test"
    ...       />''')
    >>> zope.component.getUtility(IApp, 'test') is comp
    True

Utilities can also be registered from a factory. In this case, the ZCML handler calls the factory (without any arguments) and registers the returned value as a utility. Typically, you’d pass a class for the factory:

    >>> clearZCML()
    >>> zope.component.queryUtility(IApp) is None
    True

    >>> runSnippet('''
    ...   <utility
    ...       factory="zope.component.testfiles.components.Comp"
    ...       provides="zope.component.testfiles.components.IApp"
    ...       />''')
    >>> zope.component.getUtility(IApp).__class__ is Comp
    True

### Declaring `provides` in Python

Like other directives, <utility /> can also figure out which interface a utility provides from the Python declaration:

    >>> clearZCML()
    >>> zope.component.queryUtility(IApp) is None
    True

    >>> runSnippet('''
    ...   <utility component="zope.component.testfiles.components.comp" />''')
    >>> zope.component.getUtility(IApp) is comp
    True

It won’t work if the component that is to be registered doesn’t provide anything:

    >>> clearZCML()
    >>> runSnippet('''
    ...   <utility component="zope.component.testfiles.adapter.a4" />''')
    Traceback (most recent call last):
       ...
    ZopeXMLConfigurationError: File "<string>", line 4.2-4.61
          TypeError: Missing 'provides' attribute

Or if more than one interface is provided (then the ZCML directive handler doesn’t know under which the utility should be registered):

    >>> clearZCML()
    >>> runSnippet('''
    ...   <utility component="zope.component.testfiles.adapter.a5" />''')
    Traceback (most recent call last):
       ...
    ZopeXMLConfigurationError: File "<string>", line 4.2-4.61
          TypeError: Missing 'provides' attribute

We can repeat the same drill for utility factories:

    >>> clearZCML()
    >>> runSnippet('''
    ...   <utility factory="zope.component.testfiles.components.Comp" />''')
    >>> zope.component.getUtility(IApp).__class__ is Comp
    True

    >>> runSnippet('''
    ...   <utility factory="zope.component.testfiles.adapter.A4" />''')
    Traceback (most recent call last):
       ...
    ZopeXMLConfigurationError: File "<string>", line 4.2-4.59
          TypeError: Missing 'provides' attribute

    >>> clearZCML()
    >>> runSnippet('''
    ...   <utility factory="zope.component.testfiles.adapter.A5" />''')
    Traceback (most recent call last):
       ...
    ZopeXMLConfigurationError: File "<string>", line 4.2-4.59
          TypeError: Missing 'provides' attribute

### Protected utilities

TODO:

    def testProtectedUtility(self):
        """Test that we can protect a utility.

        Also:
        Check that multiple configurations for the same utility and
        don't interfere.
        """
        self.assertEqual(zope.component.queryUtility(IV), None)
        xmlconfig(StringIO(template % (
            '''
            <permission id="tell.everyone" title="Yay" />
            <utility
              component="zope.component.testfiles.components.comp"
              provides="zope.component.testfiles.components.IApp"
              permission="tell.everyone"
              />
            <permission id="top.secret" title="shhhh" />
            <utility
              component="zope.component.testfiles.components.comp"
              provides="zope.component.testfiles.components.IAppb"
              permission="top.secret"
              />
            '''
            )))

        utility = ProxyFactory(zope.component.getUtility(IApp))
        items = getTestProxyItems(utility)
        self.assertEqual(items, [('a', 'tell.everyone'),
                                 ('f', 'tell.everyone')
                                 ])
        self.assertEqual(removeSecurityProxy(utility), comp)

    def testUtilityUndefinedPermission(self):
        config = StringIO(template % (
             '''
             <utility
              component="zope.component.testfiles.components.comp"
              provides="zope.component.testfiles.components.IApp"
              permission="zope.UndefinedPermission"
              />
            '''
            ))
        self.assertRaises(ValueError, xmlconfig, config,
                          testing=1)

## interface

The <interface /> directive lets us register an interface. Interfaces are registered as named utilities. We therefore needn’t go though all the lookup details again, it is sufficient to see whether the directive handler emits the right actions.

First we provide a stub configuration context:

    >>> import re, pprint
    >>> atre = re.compile(' at [0-9a-fA-Fx]+')
    >>> class Context(object):
    ...    actions = ()
    ...    def action(self, discriminator, callable, args):
    ...        self.actions += ((discriminator, callable, args), )
    ...    def __repr__(self):
    ...        stream = StringIO()
    ...        pprinter = pprint.PrettyPrinter(stream=stream, width=60)
    ...        pprinter.pprint(self.actions)
    ...        r = stream.getvalue()
    ...        return (''.join(atre.split(r))).strip()
    >>> context = Context()

Then we provide a test interface that we’d like to register:

    >>> from zope.interface import Interface
    >>> class I(Interface):
    ...     pass

It doesn’t yet provide `ITestType`:

    >>> from zope.component.tests.examples import ITestType
    >>> ITestType.providedBy(I)
    False

However, after calling the directive handler...

    >>> from zope.component.zcml import interface
    >>> interface(context, I, ITestType)
    >>> context
    ((None,
      <function provideInterface>,
      ('',
       <InterfaceClass __builtin__.I>,
       <InterfaceClass zope.component.tests.examples.ITestType>)),)

...it does provide `ITestType`:

    >>> from zope.interface.interfaces import IInterface
    >>> ITestType.extends(IInterface)
    True
    >>> IInterface.providedBy(I)
    True

### Navigation

- index
- modules |
- next |
- previous |
- zope.configuration 4.0 documentation »