问在应用装饰符时，在函数方法中未设置此参数

EN

export default class API {

    ...

    public async request(url_stub: string, options: any = {}): Promise<any> {
        console.log(this)
        const url = this.join_url(url_stub);
        ...
    }
}

export function log_func(_target: any,
                         name: string,
                         descriptor: PropertyDescriptor): PropertyDescriptor {
    const original_function = descriptor.value;
    descriptor.value = (... args: any[]) => {
        const parameters = args.map((a) => JSON.stringify(a)).join();
        const result = original_function.apply(this, args);
        const result_str = JSON.stringify(result);
        console.log(`Call: ${name}(${parameters}) => ${result_str}`);
        return result;
    }
    return descriptor;
}

export function uri_encode(parameter_index?: number) {
    return (_target: any,
            name: string,
            descriptor: PropertyDescriptor): PropertyDescriptor => { 
        const original_function = descriptor.value;
        descriptor.value = (... args: any[]) => {
            args = args.map((arg, index) => {
                if (parameter_index === undefined || index === parameter_index) {
                    arg = encodeURI(arg);
                }
                return arg;
            });
            const result = original_function.apply(this, args);
            return result;
        }
        return descriptor;
    }
}

    @uri_encode(0)
    @log_func
    public async request(url_stub: string, options: any = {}): Promise<any> {