Benx Blog

八月 24, 2014

Diigo Diary 08/24/2014

Filed under: Diigo Diary — benxshen @ 8:30 上午
    • We register an event element.on('$destroy', ...). What fires this $destroy event?


      There are a few special events that AngularJS emits. When a DOM node that has been compiled with Angular’s compiler is destroyed, it emits a $destroy event. Similarly, when an AngularJS scope is destroyed, it broadcasts a $destroy event to listening scopes.

    • Best Practice: Directives should clean up after themselves. You can use element.on('$destroy', ...) or scope.$on('$destroy', ...) to run a clean-up function when the directive is removed.
    • What does this transclude option do, exactly? transclude makes the contents of a directive with this option have access to the scope outside of the directive rather than inside.
    • The transclude option changes the way scopes are nested. It makes it so that the contents of a transcluded directive have whatever scope is outside the directive, rather than whatever scope is on the inside.
    • Best Practice: only use transclude: true when you want to create a directive that wraps arbitrary content.
    • We saw earlier how to use =attr in the scope option, but in the above example, we’re using &attr instead. The & binding allows a directive to trigger evaluation of an expression in the context of the original scope, at a specific time. Any legal expression is allowed, including an expression which contains a function call. Because of this, & bindings are ideal for binding callback functions to directive behaviors.
    • Best Practice: use &attr in the scope option when you want your directive to expose an API for binding to behaviors.
    • The myPane directive has a require option with value ^myTabs. When a directive uses this option, $compile will throw an error unless the specified controller is found. The ^ prefix means that this directive searches for the controller on its parents (without the ^ prefix, the directive would look for the controller on just its own element).
    • Looking back at myPane‘s definition, notice the last argument in its link function: tabsCtrl. When a directive requires a controller, it receives that controller as the fourth argument of its link function. Taking advantage of this, myPane can call the addPane function of myTabs.
    • The basic difference is that controller can expose an API, and link functions can interact with controllers using require.
    • Best Practice: use controller when you want to expose an API to other directives. Otherwise use link.

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