我该如何返回来自谷歌地图的JavaScript地理codeR回调变量？ [英] How do I return a variable from Google Maps JavaScript geocoder callback?

问题描述

我与谷歌地图API的工作，每当我变量从codeLatLng函数返回初始化函数它声称不确定。如果我从codeLatLng打印变量它显示了罚款。

I am working with the google maps API and whenever I return the variable to the initialize function from the codeLatLng function it claims undefined. If I print the variable from the codeLatLng it shows up fine.

  var geocoder;
  function initialize() {
    geocoder = new google.maps.Geocoder();
    var latlng = new google.maps.LatLng(40.730885,-73.997383);
    var addr = codeLatLng();
    document.write(addr);

  }

  function codeLatLng() {
    var latlng = new google.maps.LatLng(40.730885,-73.997383);
    if (geocoder) {
      geocoder.geocode({'latLng': latlng}, function(results, status) {
        if (status == google.maps.GeocoderStatus.OK) {
          if (results[1]) {
                return results[1].formatted_address;
          } else {
            alert("No results found");
          }
        } else {
          alert("Geocoder failed due to: " + status);
        }
      });
    }
  }

打印出未定义

如果我做的：

  var geocoder;
  function initialize() {
    geocoder = new google.maps.Geocoder();
    var latlng = new google.maps.LatLng(40.730885,-73.997383);
    codeLatLng();


  }

  function codeLatLng() {
    var latlng = new google.maps.LatLng(40.730885,-73.997383);
    if (geocoder) {
      geocoder.geocode({'latLng': latlng}, function(results, status) {
        if (status == google.maps.GeocoderStatus.OK) {
          if (results[1]) {
                document.write(results[1].formatted_address);
          } else {
            alert("No results found");
          }
        } else {
          alert("Geocoder failed due to: " + status);
        }
      });
    }
  }

打印出纽约，纽约州10012，USA

prints out New York, NY 10012, USA

推荐答案

您不能返回从函数的值，该值尚不存在，当函数返回。

You can't return the value from the function, the value doesn't exist yet when the function returns.

的地理code 方法使一个asynchonous通话，并使用一个回调来处理的结果，所以你必须做同样的在 codeLatLng 功能：

The geocode method makes an asynchonous call and uses a callback to handle the result, so you have to do the same in the codeLatLng function:

var geocoder;
function initialize() {
  geocoder = new google.maps.Geocoder();
  var latlng = new google.maps.LatLng(40.730885,-73.997383);
  codeLatLng(function(addr){
    alert(addr);
  });
}

function codeLatLng(callback) {
  var latlng = new google.maps.LatLng(40.730885,-73.997383);
  if (geocoder) {
    geocoder.geocode({'latLng': latlng}, function(results, status) {
      if (status == google.maps.GeocoderStatus.OK) {
        if (results[1]) {
          callback(results[1].formatted_address);
        } else {
          alert("No results found");
        }
      } else {
        alert("Geocoder failed due to: " + status);
      }
    });
  }
}

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