Typescript How to convert array values to class variables

Question

Suppose key is 'abc' and value 'true', I should be able to access 'this.abc'; and this should return me true

Class A {
    public someFun(){
        this.external.getData().subscribe((externalStream: Array<someType>) => {
            for(let i:number = 0; i < externalStream.length; i++){
                console.info(externalStream[i].key);    // This should be class variable
                console.info(externalStream[i].value);  // This should be above variable's value

            }
        })
    }
}

Santanu Biswas · Accepted Answer · 2017-01-26 10:49:46Z

2

Try this:

Class A {
    public someFun(){

        const obj = this;

        this.external.getData().subscribe((externalStream: Array<someType>) => {
            for(let i:number = 0; i < externalStream.length; i++){
                obj[externalStream[i].key] = externalStream[i].value;
            }
        })
    }
}

answered Jan 26, 2017 at 10:49

Santanu Biswas

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1 Comment

Mohammed Sadik Over a year ago

Awesome! This is what I was looking for!, Thank You :)

Sefe · Accepted Answer · 2017-01-26 11:05:37Z

Typescript allows you to create dictionary types (also sometimes called hash maps). This is due to the type-safe nature in Typescript where this JavaScript code is not possible:

var value = {};
value.abc = true;
for (var key in value) {
    console.info(key);
    console.info(value[key]);
}

For a type-safe approach, you would need to know about the existence of the abc property at compile-time, which you often don't. So you do this with a dictionary type:

let value: { [key: string]: boolean };
value['abc'] = true;
for (var key in value) {
    console.info(key);
    console.info(value[key]);
}

In your case that would be:

class A {
    public someFun(){
        this.external.getData().subscribe((externalStream: Array<{ [key: string]: boolean }>) => {
            for(let i:number = 0; i < externalStream.length; i++){
                for(let key in externalStream[i])  {
                    console.info(key);
                    console.info(externalStream[i][key]);
                }
            }
        })
    }
}

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