如何使用常量为对象定义通用接口？

Question

在项目中我有一些带有字符串常量的对象。例如：

export const Elements: Constants {
    DESCRIPTION: "DescriptionAutoField2",
    FORMULA_CALC: "FormulaCalcAutoField1",
    CHART_CODE: "ChartCodeAutoField1",
    CHART_CODE_DESCRIPTION: "ChartDescriptionAutoField1",
};

export const ChartAttr: Constants = {
    CHART: "Chart",
    CHART_DESCRIPTION: "ChartDescr",
};

export const SliceLink: Constants = {
    SLICE_CODE: "SliceCode",
    SLICE_DESC: "SliceDesc",
    SLICE_CALC: "SliceCalc",
};

我这样定义了接口，但在这种情况下无法在编译期间检查 Object kyes。

 export interface Constants {
       [key: string]: string;
 }

我的问题是：如何定义通用接口"Constants"并根据定义的Object属性进行严格编译？是否可以避免 "enum"?

Answer 1

没有像 Constants 这样的单一具体类型可以同时匹配所有 Elements、ChartAttr 和 SliceLink，而记住每个的确切键和值。相反，您可以表示匹配您的约束的 generic 类型，并使用辅助函数来确保值符合它，同时输出记住单个 key/value 类型的强类型值：

// helper function
const asConstants = <S extends string, T extends Record<keyof T, S>>(
    c: T
): { readonly [K in keyof T]: T[K] } => c;

我假设您希望将常量属性标记为 readonly 并且每个值的类型应该是 string literal 而不仅仅是 string.

现在您可以通过函数而不是注释来定义常量：

export const Elements = asConstants({
    DESCRIPTION: "DescriptionAutoField2",
    FORMULA_CALC: "FormulaCalcAutoField1",
    CHART_CODE: "ChartCodeAutoField1",
    CHART_CODE_DESCRIPTION: "ChartDescriptionAutoField1",
});

export const ChartAttr = asConstants({
    CHART: "Chart",
    CHART_DESCRIPTION: "ChartDescr",
});

export const SliceLink = asConstants({
    SLICE_CODE: "SliceCode",
    SLICE_DESC: "SliceDesc",
    SLICE_CALC: "SliceCalc",
});

如果您使用 IDE 的 IntelliSense 检查 Elements、ChartAttr 和 SliceLink 的类型，您会看到：

/*
const Elements: {
    readonly DESCRIPTION: "DescriptionAutoField2";
    readonly FORMULA_CALC: "FormulaCalcAutoField1";
    readonly CHART_CODE: "ChartCodeAutoField1";
    readonly CHART_CODE_DESCRIPTION: "ChartDescriptionAutoField1";
}

const ChartAttr: {
    readonly CHART: "Chart";
    readonly CHART_DESCRIPTION: "ChartDescr";
}

const SliceLink: {
    readonly SLICE_CODE: "SliceCode";
    readonly SLICE_DESC: "SliceDesc";
    readonly SLICE_CALC: "SliceCalc";
}
*/

如果您尝试将错误的值传递给 asConstants()，您会得到一个错误：

asConstants({
    NOT_A_STRING: 1, // error! number not a string        
})

好的，希望对您有所帮助。祝你好运！

Link to code

如何使用常量为对象定义通用接口？

How to define general interface for Object with constans?

typescript

typedef

type-definition