打字稿中的类型委托

Question

我有以下情况（代码片段，为简洁起见，省略了一些代码）：

export class ValidationBuilderBase implements IValidationBuilder {
    public isRequired(): IValidationBuilder {
        const validationResult = Validators.required(this.baseControl);

        if ((!isNullOrUndefined(validationResult) && !isNullOrUndefined(validationResult.required))) {
            this.baseErrors['required'] = 'This input is required.'; // a ValdationErrors instance
        }

        return this;
    }
}

export interface IValidationBuilder {
    isRequired(): IValidationBuilder;
}

export class StringValidationBuilder implements IValidationBuilder {
    constructor(private readonly builder: Validationbuilderbase) {}

    isRequired(): StringValidationBuilder {
        return this.builder.isRequired() as StringValidationBuilder;
    }
}

// other code, this is in the function
let builder = new ValidationBuilder(this.formGroup.controls['test']);
let validator: StringValidationBuilder = new StringValidationBuilder(builder);
const result = validator.isRequired(); // what should this type be? StringValidationBuilder or IValidationBuilder?

我正在使用构建器模式执行一些代码，并返回其自身的实例的位置。但是，在开发人员工具中运行代码（通过业力茉莉花测试）时，validator.isRequired()解析为类型IValidationBuilder。

我期望它在StringValidationBuilder实现接口时会导致StringValidationBuilder，但是用StringValidationBuilder覆盖返回类型，这应该是有效的吗？

我很困惑。在IDE（VsCode）中，代码完成指出返回类型应为StringValidationBuilder

编辑

我正在努力实现以下目标：

describe(`String validation chaining`, () => {
    it(`should return no errors from the (valid) chain`, () => {
        control().setValidators(Validators.required);
        control().setValue('This is some test string......');
        const result = validator
            .string
            .ifTrue((val) => false, 'error', 'should not reach here')
            .ifFalse((val) => true, 'error', 'should not reach here')
            .isRequired()
            .maxLengthAllowed(100)
            .minLengthAllowed(0)
            .range(25, 35)
            .build();

        expect(result).toEqual(null);
    });
});

我通过将代码修改为]使它正常工作>

export class StringValidationBuilder implements IValidationBuilder {
    isRequired(): StringValidationBuilder {
        this.builder.isRequired();

        return this;
    }
}

我仍然不相信这是理想的解决方案。

我有以下情况（代码片段，为简洁起见，省略了一些代码）：导出类ValidationBuilderBase实现IValidationBuilder {public isRequired（）：IValidationBuilder {...

Answer 1

怎么可能是StringValidationBuilder，您正在返回ValidationBuilderBase，因为这就是生成器。而且StringValidationBuilder没有扩展它]