Grok-like configuration for Zope browser pages
Project description
This package provides support for writing browser pages for Zope and registering them directly in Python (without ZCML).
Setting up grokcore.view
This package is essentially set up like the grokcore.component package, please refer to its documentation for details. The additional ZCML line you will need is:
<include package="grokcore.view" file="meta.zcml" /> <include package="grokcore.view" />
Put the first line somewhere near the top of your root ZCML file (but below the line where you include grokcore.component’s configuration) and the second line somewhere next to your other dependency includes.
Examples
Simple browser page
A browser page is implemented by subclassing the grokcore.view.View baseclass. At a minimum, a browser page must have
either an associated template or a render() method
a context that it’s registered for as a view
a name (which is, if not specified explicitly, the class’s name in lower case characters).
For example, the following class defines a view that’s registered for all objects and simply prints “Hello World!”:
import grokcore.view
import zope.interface
class Hello(grokcore.view.View):
grokcore.view.context(zope.interface.Interface)
def render(self):
self.response.setHeader("Content-Type", "text/plain")
return "Hello World!"
Here we’ve made use of the implicit name feature. This class will be available as the hello view for all objects. So for instance, you’ll be able to invoke it with URLs like:
http://localhost/some/obj/hello
We could also have spelled this out explicitly:
class Hello(grokcore.view.View):
grokcore.view.context(zope.interface.Interface)
grokcore.view.name('hello')
...
Browser page with template
Of course, more than often a view should render HTML which you would construct using some sort of templating engine. grokcore.view comes with built-in support for Zope’s PageTemplate engine. By convention, PageTemplate templates end with the .pt extension.
So let our Hello view render HTML instead of plain text, we remove the render() method from the class and instead we create a template, e.g. like so:
<html> <body> <p>Hello <span tal:replace="request/principal/title" />!</p> </body> </html>
This will greet a logged in user with his or her actual name.
To associate the template with the view, we have to put it in a certain place. Let’s say the Hello view class from above was in an app.py module. Then we create an app_templates directory next to it and place the template file in there (the name of this directory can be customized with the templatedir directive, see below). The file name can be anything as long as the extension is .pt. However, we can again make use of a convention here. If we name the template like the class (except in lower case characters), then the template and the class are associated automatically. If not, we would have to use the template directive on the view class to spell out the name of the template file explicitly.
To cut a long story short, if we named it app_templates/hello.pt, it would be found automatically.
Static resources
Browser pages often need additional static resources like CSS and JavaScript files. These can be conveniently placed into a directory called static in the package that contains the view code. This directory will automatically be registered as a resource directory. It is available as the static variable in all views of this package and you can refer to files inside this directory like so:
<img src="hello.png" tal:attributes="src static/hello.png" />
DirectoryResource
In addition to the very convenient “static resources”, one can use more explicitly configured and flexible DirectoryResource components. DirectoryResource component allow for differentiating resources based on layers and names and provide a way to register resources in one package and make use of these resources in another package’s views:
class FooResource(grokcore.view.DirectoryResource):
grokcore.view.path('foo')
Or with an explicit name:
class BarResource(grokcore.view.DirectoryResource):
grokcore.view.name('bar')
grokcore.view.path('bar')
Registered for a layer:
class BazResource(grokcore.view.DirectoryResource):
grokcore.view.layer(ISomeLayer)
grokcore.view.path('baz/qux')
Layers and skins
To define a browser layer, simply extend the IBrowserRequest interface:
class IGreenLayer(grokcore.view.IBrowserRequest):
pass
If you then wanted to define a skin, simply inherit from all the layer interfaces that should be in the skin and use the skin() directive to give the layer a name:
class IGreenSkin(IGreenLayer, grokcore.view.IDefaultBrowserLayer):
grokcore.view.skin('Green')
To place a view on a layer, simply use the layer directive:
class Hello(grokcore.view.View):
grokcore.view.context(zope.interface.Interface)
grokcore.view.layer(IGreenLayer)
...
API overview
Base classes
- View
Base class for browser pages. Use the context directive to specify the view’s context. Use the name directive to set the view’s name; if not used, the view’s name will be the class’s name in lower case characters. You may also use the template directive to specify the name of the template file that should be associated with the view as well as the layer directive to specify which layer it should be on if not the default layer.
View API
grokcore.view.View is a regular Zope browser page, so it behaves exactly like a regular browser page from the outside. It provides a bit more to the developer using it as a base class, though:
- context
The view’s context object. This can be discriminated by using the context directive on the view class.
- request
The request object, typically provides IBrowserRequest.
- response
The response object, typically provides IHTTPResponse.
- static
Directory resource representing the package’s static directory.
- redirect(url)
Redirect to the given URL.
- url(obj=None, name=None, data=None)
Constructs a URL:
If no arguments are given, the URL to the view itself is constructed.
If only the obj argument is given, the URL to that object is constructed.
If both obj and name arguments are supplied, construct the URL to the object and append name (presumably the name of a view).
Optionally, data can be a dictionary whose contents is added to the URL as a query string.
Methods for developers to implement:
- update(**kw)
This method will be called before the view’s associated template is rendered. If you therefore want to pre-compuate values for the template, implement this method. You can save the values on self (the view object) and later access them through the view variable from the template. The method can take arbitrary keyword parameters which are filled from request values.
- render(**kw)
Implement this method if (and only if) there isn’t a template that goes with the view class. Return either an encoded 8-bit string or a unicode string. The method can take arbitrary keyword parameters which are filled from request values.
Directives
- templatedir(dirname)
Module-level directive that tells the template machinery which directory to look in for templates that should associated with views in a particular module. If not used, it defaults to <module_name>_templates.
- template(filename_wo_ext)
Class-level directive that specifies the name a template file that’s associated with a view class, without the file extension. If not used, it defaults to the class’s name in lower case characters.
- layer(layer_interface)
Class-level directive that defines which layer the view is registered on. If not used, it defaults to the IDefaultBrowserLayer.
- skin(skin_name)
Directive used on a layer interface to register it as skin using a human-readable name (skin_name).
- path(relative_or_absolute_path)
Directove used in a DirectoryResource registration to point to a non- package directory(hierarchy) containing resources like images, css files, etc.
Other
- url(request, obj, name=None, data=None)
Generate the URL to an object, with an optional view name attached. The data argument can be a dictionary whose contents is converted into the a query string that’s appended to the URL.
- PageTemplate(template_code)
Create an inline PageTemplate object.
- PageTemplateFile(filename)
Create a PageTemplate object from a file.
- IBrowserRequest
Browser request interface from zope.publisher.
- IDefaultBrowserLayer
Default layer for browser components from zope.publisher.
In addition, the grokcore.view package exposes the grokcore.component and grokcore.security APIs.
Changes
1.2 (2008-10-16)
Expose the DirectoryResource class as a component for registering directories as resources. This is accompanied by the path directive that is used to point to the directory holding resources by way of an relative (to the module) or absolute path. DirectoryResource components can be differentiated by name and layer.
1.1 (2008-09-22)
meta.py module containing the grokkers has been split in a package with separate modules for the view, template, skin and static resources grokkers. This allows applications to use only grokkers they need (and maybe redefine others).
1.0 (2006-08-07)
Created grokcore.view in July 2008 by factoring security-related components, grokkers and directives out of Grok.
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