javascript 表达式的 Angular 惰性一次性绑定
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Angular lazy one-time binding for expressions
提问by seldary
AngularJS has a new feature since the version 1.3.0-beta.10: the "lazy one-time binding".
自 1.3.0-beta.10 版本以来，AngularJS 有一个新特性：“惰性一次性绑定”。
Simple expressions can be prefixed with ::, telling angular to stop watching after the expression was first evaluated. The common example given is something like:
简单的表达式可以以 为前缀::，告诉 angular 在表达式第一次计算后停止观看。给出的常见示例类似于：
<div>{{::user.name}}</div>
Is there a similar syntax for expressions like the following ones?
以下表达式是否有类似的语法？
<div ng-if="user.isSomething && user.isSomethingElse"></div>
<div ng-class="{classNameFoo: user.isSomething}"></div>
回答by Blackhole
Yes. You can prefix every expressions with ::, even the ones in ngIfor ngClass:
是的。您可以为每个表达式添加前缀::，甚至是ngIf或 中的表达式ngClass：
<div ng-if="::(user.isSomething && user.isSomethingElse)"></div>
<div ng-class="::{classNameFoo: user.isSomething}"></div>
Actually, the codesimply checks that the two first characters in the expression are :in order to activate the one-time binding (and then removes them, thus the parenthesis aren't even needed). Everything else remains the same.
实际上，代码只是检查表达式中的前两个字符是否:是为了激活一次性绑定（然后删除它们，因此甚至不需要括号）。其他一切都保持不变。
