AngularJs $watchGroup - 最后更改组中的哪个表达式？

Question

使用$watchGroup，如何确定组中的哪个表达式已更改

    $scope.$watchGroup(['dec','bin','oct','hex'], function(newValues, oldValues, scope) {
       last_changed = ??? //return which exp was changed in this run...
       if(last_changed=='dec') //then something
       if(last_changed=='bin') //then something
       if(last_changed=='oct') //then something
       if(last_changed=='hex') //then something
    });

编辑 1：-
--->问题是我无法从 newValues 中解除 n_vals 的绑定。

var n_vals = [];
 $scope.$watchGroup(['dec','bin','oct','hex'], function(newValues, oldValues, scope) {
  last_updated = changed_one(newValues,n_vals); //last_updated EXP
    n_vals = newValues;
 });

解决方法：-

n_vals = angular.copy(newValues);

看下面的link:
Deep copying objects in angular?

Answer 1

Angular 优惠 $watchGroup （自 1.3 起）.

基本上，它 returns 作用域变量 oldValue 和 newValue 就像我们把它放在 watchGroup.

中的方式

使用范围变量的索引获取其各自的 newVal 和 oldVal，如下所示。

获取各个作用域变量的 newValues：

newValue[0] // returns new value of dec
newValue[1] // returns new value of bin
newValue[2] // returns new value of oct
newValue[3] // returns new value of hex

获取各个作用域变量的oldValues：

oldValue[0] // returns old value of dec
oldValue[1] // returns old value of bin
oldValue[2] // returns old value of oct
oldValue[3] // returns old value of hex

$scope.$watchGroup(['dec','bin','oct','hex'], function(newValues, oldValues, scope) {
    console.log(newValues[index]); //put index value as 0(dec), 1(bin), 2(oct) or 3(hex)
    console.log(oldValues[index]); //put index value as 0(dec), 1(bin), 2(oct) or 3(hex)
});

NOTE:
Below logic is considering that only one value will change at a time.

编辑 1

要获取最后更新的变量，您可以尝试以下代码。

var arrayOfValues = ['dec', 'bin', 'oct', 'hex'];
$scope.$watchGroup(arrayOfValues, function(newValues, oldValues, scope) {
    let last_changed;

    var chanedIndex = newValues.findIndex(function(val, key){
        return val !== oldValues[key];
    });

    last_changed = arrayOfValues[chanedIndex];

    // above logic could simply avoid the below conditional logic (refer 
    // comment above in front of if condition)
    if (angular.isDefined(last_changed)) {
        // your logic will come here as per your question
        switch(last_changed){
           case 'dec':
               doSomething();
           case 'bin':
               doSomething();
           case 'oct':
               doSomething();
           case 'hex':
               doSomething();
        }
    }
});

编辑 2：

我缩小了代码并制作了

var arrayOfValues = ['dec', 'bin', 'oct', 'hex'];
// generic method which will tell you which variable has been updated
$scope.checkWhichVariableHasUpdated = fucntion(watchGroupList, newValuesObj, oldValuesObj) {
    let _lastUpdatedValue;
    angular.forEach(watchGroupList, function(value, index) {
        if (newValuesObj[index] != oldValuesObj[index])
            _lastUpdatedValue = value;
    });
    return _lastUpdatedValue;
};

$scope.mySwitchFunction = function(changedVariable) {
    switch (changedVariable) {
        case 'dec':
            doSomething();
            break;
        case 'bin':
            doSomething();
            break;
        case 'oct':
            doSomething();
            break;
        case 'hex':
            doSomething();
            break;
    }

};

$scope.$watchGroup(arrayOfValues, function(newValues, oldValues, scope) {
    var last_changed = $scope.checkWhichVariableHasUpdated(arrayOfValues, newValues, oldValues);
    if (angular.isDefined(last_changed)) {
        $scope.mySwitchFunction(last_changed)
    }
});

我希望这能解决问题。

AngularJs $watchGroup - 最后更改组中的哪个表达式？

AngularJs $watchGroup - which expression in the group was last changed?

javascript

angularjs

angularjs-service

angularjs-watch

解决方法：-