Google Distance Matrix需要返回值 [英] Google Distance Matrix need to return the value

问题描述

我已经使用Google距离矩阵API通过以下方式获取两个地理位置的最短距离:

I have using google distance matrix api to getting the shortest distance of two geo points from the following way:

<script src="https://maps.googleapis.com/maps/api/js?v=3.exp&signed_in=true"></script>
<script>

    var origin1 = new google.maps.LatLng(9.6667, 80.0000);
    var destinationA = new google.maps.LatLng(9.6689, 80.0059);



    function calculateDistances() {


        var service = new google.maps.DistanceMatrixService();
        service.getDistanceMatrix(
            {
                origins: [origin1],
                destinations: [destinationA],
                travelMode: google.maps.TravelMode.DRIVING,
                unitSystem: google.maps.UnitSystem.METRIC,
                avoidHighways: false,
                avoidTolls: false
            }, callback);

    }

    function callback(response, status) {
        if (status != google.maps.DistanceMatrixStatus.OK) {
            alert('Error was: ' + status);
        } else {
            var origins = response.originAddresses;


            for (var i = 0; i < origins.length; i++) {
                var results = response.rows[i].elements;
                for (var j = 0; j < results.length; j++) {
                    alert(results[j].distance.text);
                }
            }
        }
    }


</script>

在此代码上，我成功获得了最短的距离.但是我需要在调用方法 calculateDistances()时返回值，而不是提醒该值.我该如何使用回调方法！！

On this code I have get the shortest distance successfully. But I need to return the value when calling the method calculateDistances() instead of alert the value. How can i do in callback methods!.

推荐答案

Distance Matrix服务是异步，因此，您需要传递 callback 方法来执行完成请求后，即可处理结果.但是您可以考虑将异步API转换为 promise .

Distance Matrix service is asynchronous, for that reason, you need to pass a callback method to execute upon completion of the request, to process the results. But you could consider to convert async API to promises.

以下示例演示了如何使用jQuery将Distance Matrix服务API转换为Promise:

The following example demonstrates how to convert Distance Matrix service API to promises using jQuery:

var origin1 = new google.maps.LatLng(9.6667, 80.0000);
var destinationA = new google.maps.LatLng(9.6689, 80.0059);



function calculateDistances(origins,destinations) {
            var service = new google.maps.DistanceMatrixService();
            var d = $.Deferred();
            service.getDistanceMatrix(
                {
                    origins: origins,
                    destinations: destinations,
                    travelMode: google.maps.TravelMode.DRIVING,
                    unitSystem: google.maps.UnitSystem.METRIC,
                    avoidHighways: false,
                    avoidTolls: false
                }, 
                function(response, status){
                  if (status != google.maps.DistanceMatrixStatus.OK) {
                     d.reject(status);
                  } else {
                     d.resolve(response);
                  }
                });
            return d.promise();
}

        


        calculateDistances([origin1],[destinationA])
           .done(function(response){

                var origins = response.originAddresses;

                for (var i = 0; i < origins.length; i++) {
                    var results = response.rows[i].elements;
                    for (var j = 0; j < results.length; j++) {
                        //console.log(results[j].distance.text);
                        document.getElementById('result').innerHTML += results[j].distance.text;
                    }
                }

           })
           .fail(function(status){
              document.getElementById('result').innerHTML = 'An error occured. Status: ' + status;
           });

<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<script src="https://maps.googleapis.com/maps/api/js?signed_in=true"></script>
<div id='result'/>

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