typescript interface require one of two properties to exist

TypeScript Interface: Requiring One of Two Properties to Exist

🔍👨‍💻📝

Are you struggling with creating a TypeScript interface that requires one of two properties to exist? 🤔 Don't worry, you're not alone! It's a common issue that developers face when designing interfaces that offer flexibility without sacrificing consistency. In this blog post, we will address this specific problem and provide you with easy solutions. Let's dive in! 💪

The Interface Conundrum

The provided code snippet showcases an interface called MenuItem which represents a menu item in an application. The properties title and icon are required, while component and click are optional.

export interface MenuItem {
  title: string;
  component?: any;
  click?: any;
  icon: string;
}

Now, let's explore the two questions at hand:

1️⃣ Requiring Either component or click to be Set

If you want to ensure that either component or click is set, but not both, TypeScript allows you to achieve this by utilizing the exclusive OR (xor) operator.

export interface MenuItem {
  title: string;
  component?: any;
  click?: any;
  icon: string;
  __exclusivity?: 'component' | 'click';
}

🔑 The magic lies in the newly introduced __exclusivity property. By creating this additional property, TypeScript ensures that either component or click is present, while the other property remains undefined.

Here's how this can be used:

const menuItem1: MenuItem = {
  title: 'Example 1',
  component: ExampleComponent,
  icon: 'example-icon',
  __exclusivity: 'component',
};

const menuItem2: MenuItem = {
  title: 'Example 2',
  click: handleClick,
  icon: 'example-icon',
  __exclusivity: 'click',
};

With this approach, you have the flexibility to require either component or click to be set, providing a clear and defined structure for your code.

2️⃣ Requiring That Both Properties Can't be Set

In some cases, you may want to enforce a rule where both component and click cannot be set simultaneously. TypeScript's conditional types come to the rescue!

export interface MenuItem {
  title: string;
  component?: any;
  click?: any;
  icon: string;
  __exclusivity?: 'component' extends keyof this ? never : 'click' extends keyof this ? never : 'component' | 'click';
}

🔑 By leveraging conditional types, we can define the __exclusivity property based on whether component or click is present. If component exists, we make click ineligible, and vice versa.

Here's how this can be used:

const menuItem1: MenuItem = {
  title: 'Example 1',
  component: ExampleComponent,
  icon: 'example-icon',
};

// This will result in a TypeScript error, as both `component` and `click` are set simultaneously.
const menuItem2: MenuItem = {
  title: 'Example 2',
  component: ExampleComponent,
  click: handleClick,
  icon: 'example-icon',
};

With this solution, you can ensure that either component or click is set, never both.

Conclusion

Requiring one of two properties to exist in a TypeScript interface might initially seem challenging, but with the tips provided above, you can conquer this hurdle effortlessly. ✨💪

Remember, TypeScript offers powerful features like exclusive OR operations and conditional types that enable you to design precise and flexible interfaces.

Now it's your turn! Have you encountered this interface conundrum before? How did you solve it? Share your experiences and solutions in the comments below. Let's learn and grow together! 🌱👥💬

Keep coding, keep exploring, and never stop creating amazing interfaces! 🚀👩‍💻

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