Using TypeScript to Initialize Arrays with Objects

Question

Using TypeScript to Initialize Arrays with Objects

Why is it that in TypeScript 1.8, the following code blocks with initializers are considered legal syntax:

class A
{
    public textField: string;
}

var instanceOfClass = new A
{
    textField = "HELLO WORLD"
};

var arrayCollection = new A[]
{
    new A(), new A()
};

...but the following code block is not?

var arrayCollection = new A[]
{
    new A
    {
        textField = "HELLO"
    },
    new A
    {
        textField = "WORLD"
    }
};

It's interesting that TypeScript allows you to initialize arrays and objects, but does not support nesting object initializers within an array initializer.

arrays typescript

Answer 1

Answer №1

This code snippet contains an error in typescript syntax:

class A {
    public textField: string;
}

var instanceOfClass = new A {
    textField = "HELLO WORLD"
};

The compiler returns an error message:

Cannot find name 'textField'

To fix this issue, you can set the member value during instantiation by passing it as a constructor parameter:

class A {
    public textField: string;

    constructor(textField: string) {
        this.textField = textField;
    }
}

var instanceOfClass = new A("HELLO WORLD");

Alternatively, you can use the shorter version:

class A {
    constructor(public textField: string) {
        this.textField = textField;
    }
}

Answer 2

This code snippet contains an error in typescript syntax:

class A {
    public textField: string;
}

var instanceOfClass = new A {
    textField = "HELLO WORLD"
};

The compiler returns an error message:

Cannot find name 'textField'

To fix this issue, you can set the member value during instantiation by passing it as a constructor parameter:

class A {
    public textField: string;

    constructor(textField: string) {
        this.textField = textField;
    }
}

var instanceOfClass = new A("HELLO WORLD");

Alternatively, you can use the shorter version:

class A {
    constructor(public textField: string) {
        this.textField = textField;
    }
}

Using TypeScript to Initialize Arrays with Objects

Answer №1

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