使用TypeScript接口进行类型转换

Question

This is kind of a weird question but I'm working on a massive form containing approximately ~100 input fields. We're passing all this data to a GraphQL endpoint. We're using TypeScript and I've defined Interfaces based on the schema.

I want to know if I can use TypeScript's interface types, to be specific the type boolean, to convert certain property values automatically to true or false since they arrive from the form as strings "1" or "0" , or "true" (checkboxes)? I could then build something of a filter/converter to convert certain input types for GraphQL requests automatically when I can detect it from the Interface. There was a suggestion to do something like this, here on StackOverflow:

interface I1 {
    x: boolean; 
}

let myVar: I1['x'];

But you cannot use myVar as it is defined. I would like to get typeof I1.x so I can get back 'boolean' and then do a conversion for some fields such as .!(obj.x) etc.

So can I go about this or do I really have to generate a massive object tree converting or defining specific keys, again (duplication), to be boolean? Or do we have to think about using boolean values with GraphQ?

Answer 1

I am not aware of a way to do the conversion using only interfaces, but could you not implement the interface in a class to achieve a similar outcome? Something along the lines of:

interface IOne {
    x : boolean
}

class One implements IOne {
    constructor(b_val?: boolean, b_str?: string) {
        if (b_val): this.x = b_val
        if (b_str) {
            if (b_str == 'true')
                this.x = true
            else
                this.x = false
        }
    }
}

Then you process input with new One(true, undefined) or new One(undefined, 'true') , etc. to get the conversion done for different input types, and you can pass the resulting object directly to anything that can consume the IOne interface.