Calling functions from a typescript union type array

Question

I have a Typescript array that contains two classes

StripeCardModel | StripeBankModel

which both extend

StripePaymentModel

Now I am finding a certain class from the array that can contain two classes and then I want to use the function achAccountInterfaceObject on the found class, because if I have found that class, then it is certainly an instance of StripeBankModel .

let bankPaymentMethod = this.user.stripePaymentMethods.find( paymentMethod => paymentMethod instanceof StripeBankModel );
if ( bankPaymentMethod ) {
    this.bankAccount = bankPaymentMethod.achAccountInterfaceObject;
}

Typescript on the other hand tends to disagree with this and give me a compile time error:

Property 'achAccountInterfaceObject' does not exist on type 'StripeCardModel | StripeBankModel'.
Property 'achAccountInterfaceObject' does not exist on type 'StripeCardModel'.

Could anyone please explain to me how I can write normal code with multityped arrays in typescript without getting these compile time errors?

I have had similar problems with switch cases as like

function abc() : Foo|Boo {
    switch ( a.constructor )
    {
        case "Foo":
            a.boo();

        case "Bar":
            a.doo();
    }
}

I want to make good code, but typescript is just not letting me do this here. I dont want to break up my code into multiple functions based on class, if the classes are inherited from the same subtree or have similar functionality.

Answer 1

如果没有人提供更bankPaymentMethod解决方案，则强制转换bankPaymentMethod将抑制编译器错误。

this.bankAccount = (<StripePaymentModel>bankPaymentMethod).achAccountInterfaceObject;