AngularJs $watchGroup - 上次更改组中的哪个表达式? [英] AngularJs $watchGroup - which expression in the group was last changed?

问题描述

使用$watchGroup，如何确定组中的哪个表达式发生了变化

 $scope.$watchGroup(['dec','bin','oct','hex'], function(newValues, oldValues, scope) {last_changed = ???//返回在这次运行中改变了哪个exp...if(last_changed=='dec')//那么一些东西if(last_changed=='bin')//那么一些东西if(last_changed=='oct')//那么一些东西if(last_changed=='hex')//那么一些东西});

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 经验值n_vals = 新值；});

解决方案:-

n_vals = angular.copy(newValues);

看下面的链接:
以角度深度复制对象?

解决方案

Angular 提供 $watchGroup (自 1.3 起).

基本上，它返回作用域变量 oldValue 和 newValue，就像我们把它放在 watchGroup 中一样.

使用范围变量的索引来获取其各自的newVal 和oldVal，如下所示.

获取各个作用域变量的newValue:

newValue[0]//返回 dec 的新值newValue[1]//返回 bin 的新值newValue[2]//返回 oct 的新值newValue[3]//返回十六进制的新值

获取各个作用域变量的oldValue:

oldValue[0]//返回 dec 的旧值oldValue[1]//返回 bin 的旧值oldValue[2]//返回 oct 的旧值oldValue[3]//返回十六进制的旧值

$scope.$watchGroup(['dec','bin','oct','hex'], function(newValues, oldValues, scope) {console.log(newValues[index]);//将索引值设为 0(dec)、1(bin)、2(oct) 或 3(hex)console.log(oldValues[index]);//将索引值设为 0(dec)、1(bin)、2(oct) 或 3(hex)});

<块引用>

注意:
下面的逻辑是考虑一次只有一个值会改变.

编辑 1

要了解最后更新的是哪个变量，您可以尝试以下代码.

var arrayOfValues = ['dec', 'bin', 'oct', 'hex'];$scope.$watchGroup(arrayOfValues, function(newValues, oldValues, scope) {让 last_changed;var chanedIndex = newValues.findIndex(function(val, key){返回 val !== oldValues[key];});last_changed = arrayOfValues[chanedIndex];//上面的逻辑可以简单地避免下面的条件逻辑(参考//在 if 条件前的注释)如果(angular.isDefined(last_changed)){//你的逻辑会根据你的问题来到这里开关(last_changed){案例'dec':做点什么();案例bin":做点什么();案例八月":做点什么();案例'十六进制':做点什么();}}});

编辑 2:

我已经缩小了代码并制作了

var arrayOfValues = ['dec', 'bin', 'oct', 'hex'];//通用方法，它将告诉您哪个变量已被更新$scope.checkWhichVariableHasUpdated = fucntion(watchGroupList, newValuesObj, oldValuesObj) {让 _lastUpdatedValue;angular.forEach(watchGroupList, function(value, index) {if (newValuesObj[index] != oldValuesObj[index])_lastUpdatedValue = 值；});返回 _lastUpdatedValue;};$scope.mySwitchFunction = function(changedVariable) {开关(改变变量){案例'dec':做点什么();休息;案例bin":做点什么();休息;案例八月":做点什么();休息;案例'十六进制':做点什么();休息;}};$scope.$watchGroup(arrayOfValues, function(newValues, oldValues, scope) {var last_changed = $scope.checkWhichVariableHasUpdated(arrayOfValues, newValues, oldValues);如果(angular.isDefined(last_changed)){$scope.mySwitchFunction(last_changed)}});

我希望这能解决问题.

Using $watchGroup, how can I determine which expression in the group was changed

    $scope.$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
    });

Edit 1:-
--->the problem is i can't unbind the n_vals from the newValues.

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;
 });

Solution:-

n_vals = angular.copy(newValues);

look the following link:
Deep copying objects in angular?

解决方案

Angular offers $watchGroup (since 1.3).

Basically, it returns the scope variable oldValue and newValue in the manner how we put it in watchGroup.

Use the index of the scope variable to get its respective newVal and oldVal like below.

To get newValues of respective scope variables:

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

To get oldValues of respective scope variables:

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.

Edit 1

To catch which variable was updated last, you can try below code.

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();
        }
    }
});

Edit 2:

I have minified the code and made the

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)
    }
});

I hope this clears things up.

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