如何在指令的属性中查看属性 [英] How to watch property in attrs of directive

问题描述

我有一个控制器，它有一个不时变化的计数器.
该计数器与指令的属性相关联，并在该指令的链接函数内读取.

I have a controller that has a counter that changes from time to time.
That counter is tied to an attribute of a directive and read inside the link function of that directive.

如何让指令在每次 attr 值更改时运行函数?

How can I have a directive run a function each time that attr value changes?

谢谢.

推荐答案

在你对应的 link 函数中:(假设你的属性被称为 counter 并且你的作用域变量是:范围)

Inside your corresponding link function: (assuming your attribute is called counter and your scope variable is: scope)

scope.$watch(attrs.counter, function (newTime) {
                    //do something with the new Time
});

其他方式，当然更有效的方式:

Other way, surely more efficient way:

在您的指令中，将 scope 属性设置如下(它将被隔离):

Inside your directive, set the scope property as following (it will be isolated so):

scope: { counter: '@'}

只要调用 link 函数，就会自动观察 counter 提供的当前值.

The counter would automatically be observed providing the current value as long as the link function is called.

'@' 在这里比 '=' 更好，因为我想您没有在指令中将计数器设置为新值，这意味着您只是阅读了它.实际上，= 对于双向数据绑定更有用，但您可能不需要它.

'@' better than '=' here since you I suppose you don't set the counter to a new value in your directive, meaning you just read it. Indeed, = is more useful for two-way data binding but you might not need it.

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