16.2.1. Components and environment

NGW uses components for modularity. One python-пакет can contain one or several components. Each component inherits class Component, to load packages setuptools entry points are used.

def pkginfo():
    return dict(components=dict(
        somecomp='somepackage.somecomp'))

setup(
    name = 'somepackage',
    entry_points = {'nextgisweb.packages':
        'somepackage = somepackage:somemod:pkginfo'}
)

Each component has an ID (somecomp in an example above). The same ID is used in a class attribute identity. This ID must be unique among all packages of NGW.

To join components together instance of Env class is used, created at init. Initialization runs like this:

Component instances are created
initialize() is called for each component
configure() is called for each component

16.2.1.1. Dependencies between components

Method calls for initialize() and configure() happen in accordance with dependencies, which can be set using decorator require().

So, is you need to call initialize() of component B after A do this:

from nextgisweb.component import Component, require

class A(Component):
    identity = 'A'

    def initialize(self):
        pass

class B(Component):
    identity = 'B'

    @require('A')
    def initialize(self):
        pass

16.2.1.2. Global env object

16.2.1.3. Component class

16.2.1.4. Env class

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