当$渲染（）的ngModel真实的数据叫什么名字？ [英] When is $render() of ngModel called with real data?

问题描述

我写一个指令与ngModel合作。如示例所示，我设置$渲染控制器我在函数功能。

I am writing a directive to cooperate with ngModel. As shown in the example, I set the $render function on the controller to my function.

当的code初始化时，它与该模型的实际值调用两次，第一次用$ modelValue和$ viewValue集为NaN，然后​​在第二时间

When the code initializes, it is invoked twice, the first time with $modelValue and $viewValue set to NaN, and then a second time with the actual value of the model.

问题是，NaN的是测试一个熊。功能 isNaN（）是毫无价值的，到目前为止，我所看到的（它返回假（），但如此 [。] ）和 Number.isNaN（）未得到广泛的支持。

The problem is, NaN is a bear to test for. The function isNaN() is worthless, so far as I can see (it returns false for [""] but true for ["."]) and Number.isNaN() is not widely supported.

有什么建议？

推荐答案

的 $ modelValue 和 $ viewValue 的解决 ngModel 永远只能承担（除非特别指定） NaN的的值在最开始的 - 在链接时 - 和之前的任何 $格式化， $渲染和 $验证（按顺序）有机会运行。

The $modelValue and $viewValue of ngModel only ever assume (unless specifically assigned) the value of NaN in the very beginning - at link-time - and before any $formatters, $render and $validators (in that order) had a chance to run.

在换句话说，如果你要记录在不同的点这些价值，你会得到以下（假定 ngModel 变量设置为富）

In other words, if you were to log at various points these values, you'd get the following (assuming the ngModel variable is set to "foo"):

              link-time    $formatters     $render     $validators
              -----------------------------------------------------
$modelValue     NaN           "foo"         "foo"         "foo"
$viewValue      NaN            NaN          "foo"         "foo"

演示

在的话，除非你需要访问 ngModel 在链接 - 时间，有没有需要防范 NaN的。此外，也没有双调用 - 在 ngModel 管每变化一次运行

In words, unless you need to access ngModel at link-time, there is no need to guard against NaN. Moreover, there is also no double invocation - the ngModel pipe runs once per change.

NaN的在 $渲染函数，因为你手动调用 $渲染在链接时

Given the example you cite in comments my guess that you are seeing NaN in the $render function because you manually invoke the $render at link-time.

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