清空Angular中的输入字段(Emptying input field in Angular)

 当用户输入并且然后清除输入字段中的文本时，角度似乎具有不同的行为，具体取决于是否需要此字段。 
 
 看看这个例子 。 默认情况下，模型是user = {"name":"guest","last":"visitor"} 。 清除这两个字段时，模型变为user = {"last":""}而我会预期user = {} 。 
 
 为什么会这样？ 而且，有没有办法让两个领域的相同行为都没有使他们都（不）是必需的？ 
 
 更新： 
 
 我最后使用了手表的解决方法： 
 
$scope.$watch('user',function(newValue) {
  for (var prop in newValue) {
    if (newValue.hasOwnProperty(prop)){
      if (newValue[prop] !== undefined && newValue[prop] == "")
        newValue[prop] = undefined;
    }
  }
}, true);
 
 最有可能的是，最后一个if条件可以更有效地写，但至少它似乎按预期工作。 

Angular seems to have a different behavior when a user enters and then clears text in an input field depending if this field is required or not.
 
Take a look at this example. By default the model is user = {"name":"guest","last":"visitor"}. When clearing both fields the model becomes user = {"last":""} whereas I would have expected user = {}.
 
Why is this the case? And, is there a way to get the same behavior for both fields without making them both (not) required?
 
Update:
 
I used a workaround with watch in the end:
 
$scope.$watch('user',function(newValue) {
  for (var prop in newValue) {
    if (newValue.hasOwnProperty(prop)){
      if (newValue[prop] !== undefined && newValue[prop] == "")
        newValue[prop] = undefined;
    }
  }
}, true);
 
Most likely the last if-condition could be written more efficiently, but at least it seems to work as expected.

原文：https://stackoverflow.com/questions/33274220