Source has X element(s) but target allows only 1

user_6844481 0
Viewed 17526

The typescript compile show this error:

Source has X element(s) but target allows only 1.

export const FooMapping: [{id: FooOperation, display: string}] = [
    { id: FooOperation.Undefined, display: 'Nothing' },
    { id: FooOperation.A, display: 'I'm A' },
    { id: FooOperation.B, display: 'I'm B' }
];

export enum FooOperation {
    Undefined = 0,
    A = 1,
    B = 2,
}

What is the correct way to define an array of special object of {id: FooOperation, display: string}?

angular typescript
3 Answers

[{id: FooOperation, display: string}] defines a tuple of exactly one element.

Try:

export const FooMapping: Array<{id: FooOperation; display: string}> = [
    { id: FooOperation.Undefined, display: 'Nothing' },
    { id: FooOperation.A, display: "I'm A" },
    { id: FooOperation.B, display: "I'm B" }
];

Or think about something like:

interface Foo {
  id: FooOperation;
  display: string;
}

export const FooMapping: Foo[] = [...];
user_24366550

I had the same problem. The braces have to go after the type:

const FooMapping: [{id: FooOperation, display: string}]

should be

const FooMapping: {id: FooOperation, display: string}[]

Easy way to remember this is to replace the object with a type and see if it makes sense:

[string] doesn't work but string[] does

user_124178000 
const sendArr
    : [{
      entity: string | number | undefined,
      identifier: Array<string | Types.ObjectId | undefined>//[Types.ObjectId | string | undefined]
    }] = [{
      entity: '',
      identifier: [undefined]
    }]
user_89696020
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