Typescript types cannot be combined together

Combining Types

Is there a way to create a single type definition that incorporates the attributes of two separate types?

type BlogPost = {
    title: string
    image: {
        src: string
        width: number
        height: number
    }
    content: string
}

type BlogPostDetails {
    [detail: string]: string
}

In essence, I want blog posts to include a title, image, and content, as well as other details that are strings.

Challenge

Unfortunately, every attempt to merge these types has resulted in an error.

Property 'image' is incompatible with index signature.
Type 'image' is not assignable to type 'string'.

I've experimented with various approaches, such as:

type Post = BlogPost & BlogPostDetails

type Post = BlogPost & Record<string, string>

type Post = {
    title: string
    image: {
        src: string
        width: number
        height: number
    }
    content: string
    [detail: string]: string
}

Any thoughts or suggestions?

Answer №1

BlogPostDetails stresses the importance of all properties with a string name having a string value. However, this clashes with BlogPost, which requires an image property with an object value.

One of them must be modified to resolve this conflict.

Fortunately, Typescript excels at tailoring types to fit different scenarios and offers useful helper type functions. For instance, you can use Omit<T, K> to filter out specific properties from BlogPostDetails like this:

type Post = BlogPost & Omit<BlogPostDetails, 'image'>

For more information, check out: https://www.typescriptlang.org/docs/handbook/utility-types.html#omittype-keys

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