Angular service helps in resolving concatenate error by utilizing good practices

Question

Angular service helps in resolving concatenate error by utilizing good practices

I encountered a problem while trying to set a URL with multiple arguments. Here is the code snippet that I attempted, but it did not work as expected:

@Injectable()
export class MapService {
    ign : string = 'https://wxs.ign.fr/secret/geoportail/wmts?';
    ignEnd = '&tilematrixset=PM&tilematrix={z}&tilecol={x}&tilerow={y}';
    ignSat = this.ign + 'layer=ORTHOIMAGERY.ORTHOPHOTOS';
    this.ignSat = this.ignSat + '&tilematrixset=PM';
    this.ignSat = this.ignSat + '&Service=WMTS';
    this.ignSat = this.ignSat + '&Request=GetTile';
    this.ignSat = this.ignSat + '&Version=1.0.0';
    this.ignSat = this.ignSat + '&Format=image%2Fjpeg' + this.ignEnd;

    private LAYER_IGN_SATELLITE = {
        id: 'ignsatelite',
        name: 'IGN Satellite',
        enabled: false,
        layer: tileLayer(this.ignSat, {
            maxZoom: 20,
            attribution: 'IGN'
        })
    };

    ...
    constructor() {}
    ...

}

Upon running the code, I received the following error message:

Unexpected token. A constructor, method, accessor, or property was expected.ts(1068)

EDIT

In an attempt to troubleshoot, I tried the following fixes:

ignSat = ignSat + '&style=normal';

And also:

ignSat = this.ignSat.concat('&style=normal');

Lastly, I attempted:

this.ignSat = this.ignSat.concat('&style=normal');

https://i.sstatic.net/5WAhL.png

https://i.sstatic.net/mL9aP.png

angular typescript

Answer 1

Answer №1

Within the boundaries of a class, but outside of any specific method, you have the ability to define and potentially initialize fields. It is not permissible to redefine or reinitialize fields in this context, nor can you include arbitrary JavaScript or TypeScript statements:

class Foo {
    bar: string | undefined; // field declaration
    baz = "hello"; // field declaration and initialization

    bar = ""; // error! Cannot redeclare or reinitialize a field
    console.log("oops"); // error! Not allowed to write random code here
}

The errors you may encounter indicate that the TypeScript compiler struggles to interpret your code as either field or method declarations. For instance, it might mistakenly identify console as some member declared within Foo, leading to confusion with subsequent lines.

If you require more complex processing for a field beyond a single initializer line, it's advisable to handle such operations inside the constructor method. Remember, when working within methods, access fields by referencing them as properties of this:

class Bar {
    bar: string | undefined;
    baz = "hello";

    constructor() {
        this.bar = ""; // okay
        console.log("okay"); // okay
    }
}

In your specific case, if you need ign, ignEnd, and ignSat to behave as fields exclusive to instances of MapService (not just temporary variables), declare them as type string and carry out all necessary processing within the constructor method:

export class MapService {

    ign: string;
    ignEnd: string;
    ignSat: string;

    constructor() {
        this.ign = 'https://wxs.ign.fr/secret/geoportail/wmts?';
        this.ignEnd = '&tilematrixset=PM&tilematrix={z}&tilecol={x}&tilerow={y}';
        this.ignSat = this.ign + 'layer=ORTHOIMAGERY.ORTHOPHOTOS';
        this.ignSat = this.ignSat + '&tilematrixset=PM';
        this.ignSat = this.ignSat + '&Service=WMTS';
        this.ignSat = this.ignSat + '&Request=GetTile';
        this.ignSat = this.ignSat + '&Version=1.0.0';
        this.ignSat = this.ignSat + '&Format=image%2Fjpeg' + this.ignEnd;

    }
   
}

Explore the code on TypeScript Playground

Answer 2

Within the boundaries of a class, but outside of any specific method, you have the ability to define and potentially initialize fields. It is not permissible to redefine or reinitialize fields in this context, nor can you include arbitrary JavaScript or TypeScript statements:

class Foo {
    bar: string | undefined; // field declaration
    baz = "hello"; // field declaration and initialization

    bar = ""; // error! Cannot redeclare or reinitialize a field
    console.log("oops"); // error! Not allowed to write random code here
}

The errors you may encounter indicate that the TypeScript compiler struggles to interpret your code as either field or method declarations. For instance, it might mistakenly identify console as some member declared within Foo, leading to confusion with subsequent lines.

If you require more complex processing for a field beyond a single initializer line, it's advisable to handle such operations inside the constructor method. Remember, when working within methods, access fields by referencing them as properties of this:

class Bar {
    bar: string | undefined;
    baz = "hello";

    constructor() {
        this.bar = ""; // okay
        console.log("okay"); // okay
    }
}

In your specific case, if you need ign, ignEnd, and ignSat to behave as fields exclusive to instances of MapService (not just temporary variables), declare them as type string and carry out all necessary processing within the constructor method:

export class MapService {

    ign: string;
    ignEnd: string;
    ignSat: string;

    constructor() {
        this.ign = 'https://wxs.ign.fr/secret/geoportail/wmts?';
        this.ignEnd = '&tilematrixset=PM&tilematrix={z}&tilecol={x}&tilerow={y}';
        this.ignSat = this.ign + 'layer=ORTHOIMAGERY.ORTHOPHOTOS';
        this.ignSat = this.ignSat + '&tilematrixset=PM';
        this.ignSat = this.ignSat + '&Service=WMTS';
        this.ignSat = this.ignSat + '&Request=GetTile';
        this.ignSat = this.ignSat + '&Version=1.0.0';
        this.ignSat = this.ignSat + '&Format=image%2Fjpeg' + this.ignEnd;

    }
   
}

Explore the code on TypeScript Playground

Answer 3

Answer №2

When it comes to TypeScript (similar to JS), declaring variables involves using the keyword let along with an optional type specifier. If you need to concatenate strings, there are a few methods to achieve this - you can use the overloaded + operator, utilize the .concat method on strings, or explore the concept of JS template literals. Below is an adjusted version of your example that functions perfectly (Playground Link):

let ign: string = 'https://wxs.ign.fr/secret/geoportail/wmts?';
let ignEnd: string = '&tilematrixset=PM&tilematrix={z}&tilecol={x}&tilerow={y}';
let ignSat: string = ign + 'layer=ORTHOIMAGERY.ORTHOPHOTOS';
ignSat = ignSat + '&tilematrixset=PM';
ignSat = ignSat + '&Service=WMTS';
ignSat = ignSat + '&Request=GetTile';
ignSat = ignSat + '&Version=1.0.0';
ignSat = ignSat + '&Format=image%2Fjpeg' + ignEnd;

If I overlooked any details, feel free to provide further clarification in your question.

Answer 4

When it comes to TypeScript (similar to JS), declaring variables involves using the keyword let along with an optional type specifier. If you need to concatenate strings, there are a few methods to achieve this - you can use the overloaded + operator, utilize the .concat method on strings, or explore the concept of JS template literals. Below is an adjusted version of your example that functions perfectly (Playground Link):

let ign: string = 'https://wxs.ign.fr/secret/geoportail/wmts?';
let ignEnd: string = '&tilematrixset=PM&tilematrix={z}&tilecol={x}&tilerow={y}';
let ignSat: string = ign + 'layer=ORTHOIMAGERY.ORTHOPHOTOS';
ignSat = ignSat + '&tilematrixset=PM';
ignSat = ignSat + '&Service=WMTS';
ignSat = ignSat + '&Request=GetTile';
ignSat = ignSat + '&Version=1.0.0';
ignSat = ignSat + '&Format=image%2Fjpeg' + ignEnd;

If I overlooked any details, feel free to provide further clarification in your question.

Angular service helps in resolving concatenate error by utilizing good practices

Answer №1

Answer №2

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