无法读取lat undefined的属性

Question

我真不知道为什么会出现这种情况。

这是我的谷歌地图脚本标签：

<script src="https://maps.googleapis.com/maps/api/js?v=3.exp&libraries=places,geometry"></script>

如下所示，我已将纬度定义为lat（）。它将错误指向第120行，即distanceInMeters

  openMapPage()
  { 

    // GETTING THE CURRENT USER ADDRESS FOR LATITUDE AND LONGTITUDE
    var uid = firebase.auth().currentUser.uid;
    var ref = firebase.database().ref("request/" + uid);
    ref.once("value").then((snapshot) => { // <------ Here!
        var a = snapshot.exists();  // true
        var c = snapshot.hasChild("reqdetails"); // true
        var d = snapshot.child('reqdetails').exists();
        var requestsKey = snapshot.key;
        var requestsValue = snapshot.val();


       ref.once('value', (request) => {
  var currentUserAddress = request.val().regdetails.address;
  var geocoder = new google.maps.Geocoder();

  geocoder.geocode( { 'address': currentUserAddress}, function(results, status) {
    if (status == google.maps.GeocoderStatus.OK) {
      var latitude = results[0].geometry.location.lat();
      var longitude = results[0].geometry.location.lng();
      var latlng = new LatLng(latitude, longitude);
      var meterLimit  = latlng;
      //var userAddress = new LatLng(currentUserAddress);
      console.log("SURESH IS COOL");
      console.log(meterLimit);

    } 
  }); 

});           

//END OF CURRENT USER 
}); 


  // GETTING THE ALL  USER ADDRESS FOR LATITUDE AND LONGTITUDE
    var ref1 = firebase.database().ref("request");
    ref1.once("value").then((snapshot1) => { // <------ Here!
        var a = snapshot1.exists();  // true
        var c = snapshot1.hasChild("reqdetails"); // true
        var d = snapshot1.child('reqdetails').exists();
        var requestsKey = snapshot1.key;
        var requestsValue = snapshot1.val();


        snapshot1.forEach((childSnapshot) => { // <------ And here!
            var requestKey = childSnapshot.key;
            var requestValue = childSnapshot.val();
            var reqdetails = requestValue.reqdetails;
            var AllUserAddress = requestValue.regdetails.address;

            //console.log("ALL USER ADDRESS");
            //console.log(AllUserAddress);

        var geocoder1 = new google.maps.Geocoder();

  geocoder1.geocode( { 'address': AllUserAddress}, function(results, status) {
    if (status == google.maps.GeocoderStatus.OK) {
      var latitude1 = results[0].geometry.location.lat();
      var longitude1 = results[0].geometry.location.lng();
      var latlng1 = new LatLng(latitude1, longitude1);
      //var userAddress = new LatLng(currentUserAddress);
      //console.log("SURESH IS COOL");
      //console.log(latlng1);
      var distanceInMeters = google.maps.geometry.spherical.computeDistanceBetween (this.latlng, this.latlng1);
      console.log("DISTANCE");
      console.log(distanceInMeters);


    } 
  }); 



        });

    });







  }

错误看起来像这样，它一直在说lat。我的代码没有错误。顺便说一句，错误线120没有错误。

我仍然可以控制日志所有用户地址lat和lng

Answer 1

我认为情况是您尚未在全局范围内定义this.latlng, this.latlng1，因此无法访问它们，您尝试访问函数内声明的局部变量这就是为什么你无法获得distanceInMeters的原因。所以试试这个：

public latlng; // DECLARE THEM ABOVE THE CONSTRUCTOR OF YOUR CLASS
public latlng1;

constructor(){
}

/* 
  DO THE FOLLOWING TO BOTH YOUR GEOCODERS:
  - GET BOTH LATITUDE AND LONGITUDE OF YOUR.
  - ACCESS YOUR GLOBAL latlng WITH this.
*/
geocoder1.geocode( { 'address': AllUserAddress}, function(results, status) {
  if (status == google.maps.GeocoderStatus.OK) {
    let latitude1 = results[0].geometry.location.lat();
    let longitude1 = results[0].geometry.location.lng();
    this.latlng1 = new LatLng(latitude1, longitude1);
    let distanceInMeters = google.maps.geometry.spherical.computeDistanceBetween (this.latlng, this.latlng1);
    console.log("DISTANCE");
    console.log(distanceInMeters);
  } 
});

希望这有帮助