How can I retrieve Map<K, V> values from JSON in a DTO?

Question

How can I retrieve Map<K, V> values from JSON in a DTO?

I am currently dealing with a situation where I have nested DTOs as follows:

export class firstDTO {
    public data: secondDTO;
}

export class secondDTO{
    public data: Map<Color, thirdDTO>;
}

When I receive the JSON data from the backend and try to print it to the console, I am facing difficulties accessing the values inside the Map. I keep encountering undefined errors.

private getJsonData(): void {
this.service.getJSON()
  .subscribe((jsonData: firstDTO) => {
    this.things = jsonData;
  });
}

The way I would ideally like to access a property of Color is by using this syntax:

this.things.data.data.key[0].property

However, I understand that this approach won't work, so I am seeking assistance in resolving this issue.

angular typescript collections frontend

Answer 1

Answer №1

If the retrieved JSON matches the type of the first DTO and you have the key for the third DTO, you can access it as shown below in the print method. Otherwise, you can iterate through data.first.second to return a map with keys and values as ThirdDTO. The maps can be iterated using a foreach loop.

export class AppComponent {
print(data:first){
console.log(data.first.second.get('color'));
}
}

class first{
first:second;
}

class second{
second:Map<string,third>;
}

class third{
third:string;
}

Answer 2

If the retrieved JSON matches the type of the first DTO and you have the key for the third DTO, you can access it as shown below in the print method. Otherwise, you can iterate through data.first.second to return a map with keys and values as ThirdDTO. The maps can be iterated using a foreach loop.

export class AppComponent {
print(data:first){
console.log(data.first.second.get('color'));
}
}

class first{
first:second;
}

class second{
second:Map<string,third>;
}

class third{
third:string;
}

Answer 3

Answer №2

JSON does not contain Map objects. It seems like what you have is an object meant to be accessed with strings in the form of LocationDTO(...). To declare this, do the following:

export class secondDTO{
    public data: {[s: string]: thirdDTO};
}

If key[0] follows the correct format as a string, then you should use

this.things.data.data[key[0]].property

to retrieve a property from the third DTO. Make sure to notice the extra square brackets instead of a dot.

Answer 4

JSON does not contain Map objects. It seems like what you have is an object meant to be accessed with strings in the form of LocationDTO(...). To declare this, do the following:

export class secondDTO{
    public data: {[s: string]: thirdDTO};
}

If key[0] follows the correct format as a string, then you should use

this.things.data.data[key[0]].property

to retrieve a property from the third DTO. Make sure to notice the extra square brackets instead of a dot.

How can I retrieve Map<K, V> values from JSON in a DTO?

Answer №1

Answer №2

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