你可以解析angularjs承诺返回前？ [英] Can you resolve an angularjs promise before you return it?

问题描述

我想写一个返回承诺的功能。但有些时候，请求的信息立即可用。我想将它包装在一个承诺使消费者并不需要做出决定。

I am trying to write a function that returns a promise. But there are times when the information requested is available immediately. I want to wrap it in a promise so that the consumer doesn't need to make a decision.

function getSomething(id) {
    if (Cache[id]) {
        var deferred = $q.defer();
        deferred.resolve(Cache[id]); // <-- Can I do this?
        return deferred.promise;
    } else {
        return $http.get('/someUrl', {id:id});
    }
}

和使用这样的：

somethingService.getSomething(5).then(function(thing) {
    alert(thing);
});

的问题是，回调不执行为$ P $对解决的承诺。这是做合法的事情吗？有没有更好的方式来处理这种情况？

The problem is that the callback does not execute for the pre-resolved promise. Is this a legitimate thing to do? Is there a better way to handle this situation?

推荐答案

简短的回答：是的，你可以解析AngularJS答应你回到它之前，它会表现为你所期望的。

Short answer: Yes, you can resolve an AngularJS promise before you return it, and it will behave as you'd expect.

从 JB Nizet的Plunkr但重构到了最初要求的范围内正常工作（即一个函数调用服务），实际上在现场。

From JB Nizet's Plunkr but refactored to work within the context of what was originally asked (i.e. a function call to service) and actually on site.

里面的服务...

function getSomething(id) {
    // There will always be a promise so always declare it.
    var deferred = $q.defer();
    if (Cache[id]) {
        // Resolve the deferred $q object before returning the promise
        deferred.resolve(Cache[id]); 
        return deferred.promise;
    } 
    // else- not in cache 
    $http.get('/someUrl', {id:id}).success(function(data){
        // Store your data or what ever.... 
        // Then resolve
        deferred.resolve(data);               
    }).error(function(data, status, headers, config) {
        deferred.reject("Error: request returned status " + status); 
    });
    return deferred.promise;

}

在控制器....

somethingService.getSomething(5).then(    
    function(thing) {     // On success
        alert(thing);
    },
    function(message) {   // On failure
        alert(message);
    }
);

我希望它可以帮助别人。我没有找到其他的答案很清楚。

I hope it helps someone. I didn't find the other answers very clear.

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