Typescript Init Dynamic Class Call By Name (2345)

How can I call a class without resorting to conditional statements? problem: (parameter) item: inputs Argument of type 'inputs' is not assignable to parameter of type 'ISelect &

Solution 1:

because the b is a union of inputs you need to narrow it again in the map function, unfortunately it's a limitation of typescript.

let a = b.map(item =>
    item.type === 'inputSelect' ? new classes[item.type](item) : 
    item.type === 'inputText' ? new classes[item.type](item) : 
    undefined
);

or you can do a dynamic type check, then you need only 1 condition on any amount of interfaces in the inputs union.

const checker = <T extends inputs>(item: T, cl: unknown): cl is ({new (a: T): InstanceType<(typeof classes)[T['type']]>}) => { 
    return classes[item.type] === cl;
};

let a = b.map(item => {
    const cl = classes[item.type];
    returnchecker(item, cl) ? newcl(item) : undefined;
}).filter((v): v is NonNullable<typeof v> => !!v);