Google Maps Places Autocomplete - Uncaught TypeError: Cannot read property 'getPlace' of undefined

Question

setAutocomplete() {
    this.originPlaceId = null;
    this.destinationPlaceId = null;
    this.travelMode = google.maps.TravelMode.WALKING;
    this.directionsDisplay.setMap(this.map);

    this.setMapControls(this.map);

    this.setupClickListener('changemode-walking', google.maps.TravelMode.WALKING);
    this.setupClickListener('changemode-transit', google.maps.TravelMode.TRANSIT);
    this.setupClickListener('changemode-driving', google.maps.TravelMode.DRIVING);

    console.log(this.originInput);
    this.originAutocomplete = new google.maps.places.Autocomplete(this.originInput);
    this.originAutocomplete.bindTo('bounds', this.map);
    console.log(this.originAutocomplete);
    this.originAutocomplete.addListener('place_changed', function() {
        console.log(this.originAutocomplete);
        var place = this.originAutocomplete.getPlace();
        console.log("here", place);
        if (!place.geometry) {
            window.alert("Autocomplete's returned place contains no geometry");
            return;
        }
        this.expandViewportToFitPlace(this.map, place);

        // If the place has a geometry, store its place ID and route if we have
        // the other place ID
        this.originPlaceId = place.place_id;
        this.route(this.directionsService, this.directionsDisplay);
    });

    this.destinationAutocomplete = new google.maps.places.Autocomplete(this.destinationPlaceInput);
    this.destinationAutocomplete.bindTo('bounds',this.map);
    this.destinationAutocomplete.addListener('place_changed', function() {
        var place = this.destinationAutocomplete.getPlace();
        if (!place.geometry) {
            window.alert("Autocomplete's returned place contains no geometry");
            return;
        }
        this.expandViewportToFitPlace(this.map, place);

        // If the place has a geometry, store its place ID and route if we have
        // the other place ID
        this.destinationPlaceId = place.place_id;
        this.route(this.directionsService, this.directionsDisplay);
        //this.getNearbyPlaces(this.destinationPlaceId, 5000);
    });
};

setMapControls(map) {
    this.originInput = document.getElementById('origin-input');
    this.destinationPlaceInput = document.getElementById('destination-input');
    this.modes = document.getElementById('mode-selector');

    map.controls[google.maps.ControlPosition.TOP_LEFT].push(this.originInput);
    map.controls[google.maps.ControlPosition.TOP_LEFT].push(this.destinationPlaceInput);
    map.controls[google.maps.ControlPosition.TOP_LEFT].push(this.modes);
};

<input id="origin-input" class="controls" type="text" force-selection="true" placeholder="Enter an origin location">
<input id="destination-input" class="controls" type="text" force-selection="true" placeholder="Enter a destination location">
<div id="mode-selector" class="controls">
    <input type="radio" name="type" id="changemode-walking" checked="checked">
    <label for="changemode-walking">Walking</label>
    <input type="radio" name="type" id="changemode-transit">
    <label for="changemode-transit">Transit</label>
    <input type="radio" name="type" id="changemode-driving">
    <label for="changemode-driving">Driving</label>
</div>
<div id="directionsList"></div>
<div id="map_canvas"></div>

我有这些函数，这些函数应该从 Google 地图位置从输入字段（originInput 和 destinationPlaceInput）给我方向 A 到 B。

在我 select 输入后，我在控制台中出现此错误：

Uncaught TypeError: Cannot read property 'getPlace' of undefined

此错误在 "place_changed" 事件触发后抛出。

Answer 1

在 place_changed-回调中，关键字 this 指向已触发事件的对象。

所以你可以简单地使用

var place = this.getPlace();

而不是

var place = this.destinationAutocomplete.getPlace();

Answer 2

如何保持控制器的上下文/`this`？

tldr:

创建一个函数，returns一个具有上下文的函数：

this.searchBox.addListener('places_changed', ((that) => () => this.placesChanged(that))(this));

说明

如Dr.Molle指出：this指向触发事件的对象，即要添加事件监听器的元素。

addListener 采用函数声明。要继续访问控制器的 this，您还可以创建一个闭包，将控制器的 this 传递到函数中，如下所示：

this.searchBox.addListener('places_changed', ((that) => () => this.placesChanged(that))(this));

我在这里定义了一个函数，它接受一个名为 that 的参数，并且在执行时 returns 一个包含 this 的函数。它是一个闭包，因为内部函数的范围保留了对来自外部函数范围的 that 变量的引用（以及可以传递给 this.placesChanged 的其他变量）。

现在，如果发出事件 places_changed，则函数声明为运行。我仍然能够在 this.placesChanged 函数内更改 that 变量的属性。这是可能的，因为 in 对象是通过引用传递的（而原始类型是通过值传递的）。

Google Maps Places Autocomplete - Uncaught TypeError: Cannot read property 'getPlace' of undefined