Show details on map click with Angular's OpenLayers integration

Question

Show details on map click with Angular's OpenLayers integration

When working with an Angular2 component, I am trying to retrieve the element id on a click event on an OpenLayers map within the ngOnInit function. Below is the code I am using:

map.on("click", (e) => {
    map.forEachFeatureAtPixel(e.pixel, function (feature, layer) {
        let id: number = feature.getId();
        this.myService.getFeatureDetail(id)
          .suscribe(data => this.myArray = data)
    })
});

Unfortunately, I am encountering an error when clicking on the map that states I cannot call the function 'getFeatureDetail' of undefined. I have also attempted to save the id in a global variable, but this does not resolve the issue.

javascript angular typescript onclick openlayers-3

Answer 1

Answer №1

Consider utilizing arrow functions (=>) instead of typing out the function keyword. Arrow functions effectively capture the meaning of the 'this' keyword.

 map.on("click", (e) => {
     map.forEachFeatureAtPixel(e.pixel, (feature, layer) => {
         // Your code here
     }) 
 });

Answer 2

Consider utilizing arrow functions (=>) instead of typing out the function keyword. Arrow functions effectively capture the meaning of the 'this' keyword.

 map.on("click", (e) => {
     map.forEachFeatureAtPixel(e.pixel, (feature, layer) => {
         // Your code here
     }) 
 });

Answer 3

Answer №2

The issue lies in the fact that the value of this is being lost in your callback scope, as it is referencing a different object that does not contain an instance of myService.

If you save a reference to your advice object in another variable (_this, self, me, etc.), you can use that variable later on.

For more information, refer to this link.

map.on("click", (e) => {
        var _this = this;
        map.forEachFeatureAtPixel(e.pixel, function (feature, layer) {
            let id: number = feature.getId();
            _this.myService.getFeatureDetail(id)
              .subscribe(data => this.myArray = data)
        })
    });

@Fatal's answer works because the Lambda (Fat arrow) function does the same thing (when compiled into ES5), and yes, it is the most convenient approach for this scenario.

However, understanding what is happening behind the scenes is essential in certain situations.

Take a moment to read this quick (2 min read) article as well.

Answer 4

The issue lies in the fact that the value of this is being lost in your callback scope, as it is referencing a different object that does not contain an instance of myService.

If you save a reference to your advice object in another variable (_this, self, me, etc.), you can use that variable later on.

For more information, refer to this link.

map.on("click", (e) => {
        var _this = this;
        map.forEachFeatureAtPixel(e.pixel, function (feature, layer) {
            let id: number = feature.getId();
            _this.myService.getFeatureDetail(id)
              .subscribe(data => this.myArray = data)
        })
    });

@Fatal's answer works because the Lambda (Fat arrow) function does the same thing (when compiled into ES5), and yes, it is the most convenient approach for this scenario.

However, understanding what is happening behind the scenes is essential in certain situations.

Take a moment to read this quick (2 min read) article as well.

Show details on map click with Angular's OpenLayers integration

Answer №1

Answer №2

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