Summary:
adds `this.context` which you can think of as implicit props, which are passed automatically down the //ownership// hierarchy.
Contexts should be used sparingly, since they essentially allow components to communicate with descendants (in the ownership sense, not parenthood sense), which is not usually a good idea. You probably would only use contexts in places where you'd normally use a global, but contexts allow you to override them for certain view subtrees which you can't do with globals.
The context starts out `null`:
var RootComponent = React.createClass({
render: function() {
// this.context === null
}
});
You should **never** mutate the context directly, just like props and state.
You can change the context of your children (the ones you own, not `this.props.children` or via other props) using the new `withContext` method on `React`:
var RootComponent = React.createClass({
render: function() {
// this.context === null
var children = React.withContext({foo: 'a', bar: 'b'}, () => (
// In ChildComponent#render, this.context === {foo: 'a', bar: 'b'}
<ChildComponent />
));
// this.context === null
}
});
Contexts are merged, so a component can override its owner's context **for its children**:
var ChildComponent = React.createClass({
render: function() {
// this.context === {foo: 'a', bar: 'b'} (for the caller above)
var children = React.withContext({foo: 'c'},() => (
// In GrandchildComponent#render,
// this.context === {foo: 'c', bar: 'b'}
<GrandchildComponent />
));
// this.context === {foo: 'a', bar: 'b'}
}
});
This adds a `toBeComponentOfType` method to `reactComponentExpect`. Now that we are injecting composite native components, `toBeDOMComponentWithTag` will not suffice and should be deprecated.
Marshall Roch
CommitSyncScript
Paul O’Shannessy