I am facing an issue with my interface - the variable designed to store boolean values

Something unusual happened with Typescript - I assigned a string value to a boolean variable, but no error was generated.

I purposely triggered an error in order to observe how Typescript would react, only to find that it did not produce the expected error message.

To investigate further, I created a class with a boolean attribute, then defined an interface and a constructor method to initialize the variable. However, when I received a JSON object with the variable as type string, the boolean variable accepted the string value without any errors being raised. This goes against the intended data type validation in my code.

export class Product{

    public status:boolean;

    constructor(obj?: IProduct) { 

        if(obj)
        {
            this.status = obj.status;
        }
    }

}

interface IProduct {
    status:boolean;
}

In the JSON response from the server:

{status: "test"}

The 'test' string is incorrectly being allocated to the boolean 'status' variable.

Is there a way to enforce strict type checking for this variable to ensure it only accepts boolean values? Any insights or suggestions are greatly appreciated.

Answer №1

Runtime lacks type enforcement capability.

Try using Decorators as a potential solution:

class Item {
    @validate
    public availability: boolean;

    constructor(obj?: IItem) { 
        if(obj) {
            this.availability = obj.status;
        }
    }
}

interface IItem {
    status: string;
}

function validate(target: any, propertyKey: string) : any {
    if (propertyKey === "status") {
        return {
            set: function (value: any) {
                if (typeof value !== "boolean") {
                    throw new Error("The value provided is not of boolean type");
                }
            }
        }
    }
}

Answer №2

Perhaps the issue is related to your User Interface

interface IProduct { // correction: it should be IProduct
    name:boolean; // and this should probably be name instead of nome
}

If you want to ensure that all values have specified types, you can set noImplicitAny to true in tsconfig.json, which applies to TypeScript classes.

Answer №3

Here's a suggestion:

interface IProduct {
    availability: boolean;
}

Correct the interface typo and update 'nome' to 'availability'.

Answer №4

Implement the following conditional statement within your constructor method:

if (typeof variable !== 'string') {
    throw new Error('Variable must be of type string');
}

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