React.js，在触发函数之前等待setState完成?

问题描述：

这是我的情况:

在this.handleFormSubmit()上，我正在执行this.setState()
在this.handleFormSubmit()内部，我叫this.findRoutes(); -取决于this.setState()的成功完成
this.setState();在this.findRoutes之前无法完成...
在调用this.findRoutes()之前，如何等待this.handleFormSubmit()内部的this.setState()完成?

on this.handleFormSubmit() I am executing this.setState()
inside this.handleFormSubmit(), I am calling this.findRoutes(); - which depends on the successful completion of this.setState()
this.setState(); does not complete before this.findRoutes is called...
How do I wait for this.setState() inside of this.handleFormSubmit() to finish before calling this.findRoutes()?

不合格的解决方案:

将this.findRoutes()放入componentDidUpdate()
这是不可接受的，因为将有更多与findRoutes()函数无关的状态更改.我不想在不相关的状态更新时触发findRoutes()函数.

请参见下面的代码段

handleFormSubmit: function(input){
                // Form Input
                this.setState({
                    originId: input.originId,
                    destinationId: input.destinationId,
                    radius: input.radius,
                    search: input.search
                })
                this.findRoutes();
            },
            handleMapRender: function(map){
                // Intialized Google Map
                directionsDisplay = new google.maps.DirectionsRenderer();
                directionsService = new google.maps.DirectionsService();
                this.setState({map: map});
                placesService = new google.maps.places.PlacesService(map);
                directionsDisplay.setMap(map);
            },
            findRoutes: function(){
                var me = this;
                if (!this.state.originId || !this.state.destinationId) {
                    alert("findRoutes!");
                    return;
                }
                var p1 = new Promise(function(resolve, reject) {
                    directionsService.route({
                        origin: {'placeId': me.state.originId},
                        destination: {'placeId': me.state.destinationId},
                        travelMode: me.state.travelMode
                    }, function(response, status){
                        if (status === google.maps.DirectionsStatus.OK) {
                            // me.response = response;
                            directionsDisplay.setDirections(response);
                            resolve(response);
                        } else {
                            window.alert('Directions config failed due to ' + status);
                        }
                    });
                });
                return p1
            },
            render: function() {
                return (
                    <div className="MapControl">
                        <h1>Search</h1>
                        <MapForm
                            onFormSubmit={this.handleFormSubmit}
                            map={this.state.map}/>
                        <GMap
                            setMapState={this.handleMapRender}
                            originId= {this.state.originId}
                            destinationId= {this.state.destinationId}
                            radius= {this.state.radius}
                            search= {this.state.search}/>
                    </div>
                );
            }
        });

答

setState()具有可用于此目的的可选回调参数.您只需要对此稍作更改即可.

setState() has an optional callback parameter that you can use for this. You only need to change your code slightly, to this:

// Form Input
this.setState(
  {
    originId: input.originId,
    destinationId: input.destinationId,
    radius: input.radius,
    search: input.search
  },
  this.findRoutes         // here is where you put the callback
);

请注意，对findRoutes的调用现在位于setState()调用中，作为第二个参数.
不使用()，因为您正在传递函数.

Notice the call to findRoutes is now inside the setState() call, as the second parameter.
Without () because you are passing the function.

React.js，在触发函数之前等待setState完成?

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