英文:
How do I dynamically add attributes to an interface in typescript?
问题
可以在 TypeScript 中实现上面的需求，以下是代码示例：
type Add<T, K, V> = T & { [P in K]: V };
interface Container { }
type ResultContainer = Add<Container, "name", string>;
type FinalContainer = Add<ResultContainer, "age", number>;
这将创建一个名为 FinalContainer 的接口，它包含了所需的属性 name 和 age。
英文:
I have an interface：
interface Container {
}
// I want to do the following
Add<Container, "name", string>
Add<Container, "age", number>
// Here are the results I hope to get
interface Container {
name: string
age: number
}
Is it possible to implement the above in typescript?
答案1
得分: 0
以下是翻译好的内容：
不可能以 Add<T, K, V> 形式的内容修改传递给 T 的类型参数的声明，无论 Add 是否是一个泛型类型（例如，type Add<T, K, V> = ⋯; type Foo = Add<Container, "name", string>;）还是一个实例化表达式（例如，function Add<T, K, V>(⋯){⋯}; const foo = Add<Container, "name", string>;）
TypeScript 提供的唯一修改现有接口类型声明的方式是通过声明合并，在其中重新声明接口并添加新属性：
interface Container { name: string }
// 稍后
interface Container { age: number }
const c: Container = { name: "abc", age: 123 }; // 可行
c.name.toUpperCase(); // 可行
c.age.toFixed(); // 可行
但没有办法使用用户定义的代码来抽象出声明合并操作。我找不到关于这方面的任何现有功能请求在TypeScript的问题列表中，所以我无法指向一个官方来源来证明这是不可能的。如果有人提出这样的问题，那么我们可以听取来自TypeScript团队的官方回应，但我想这个问题很可能会被迅速拒绝。
英文:
It is not possible for something of the form Add<T, K, V> to modify the declaration of the type argument passed in as T, whether Add is a generic type (e.g., type Add<T, K, V> = ⋯; type Foo = Add<Container, "name", string>;) or an instantiation expression (e.g., function Add<T, K, V>(⋯){⋯}; const foo = Add<Container, "name", string>;)
The only facility TypeScript provides to modify the declaration of an existing interface type is via declaration merging, where you re-declare the interface and add new properties to it:
interface Container { name: string }
// later
interface Container { age: number }
const c: Container = { name: "abc", age: 123 }; // okay
c.name.toUpperCase(); // okay
c.age.toFixed(); // okay
But there is no way to abstract over the declaration merging operation with user-defined code. I can't find any existing feature request for this in TypeScript's issue list, so I can't direct you to an authoritative source saying this is impossible. If one were to file such an issue then we could hear official word from the TypeScript team, but I imagine the issue would be swiftly declined.
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