芭蕾舞服务等级中从*开始的字段是什么

Question

请检查 Ballerina 中定义的以下服务类别。

service class RequestInterceptor {
    *http:RequestInterceptor;

    // A default resource function, which will be executed for all the requests. 
    // A `RequestContext` is used to share data between the interceptors.
    // An accessor and a path can also be specified. In that case, the interceptor will be
    // executed only for the requests, which match the accessor and path.
    resource function 'default [string... path](http:RequestContext ctx, 
                        http:Request req) returns http:NextService|error? {
        // Sets a header to the request inside the interceptor service.
        req.setHeader(interceptor_header, interceptor_header_value);
        // Returns the next interceptor or the target service in the pipeline. 
        // An error is returned when the call fails.
        return ctx.next();
    }
}

在上面的服务类中，有一个从

*

开始的字段。 （即

*http:RequestInterceptor;

）。

这种特殊的字段有什么用？

Answer 1

这是对象类型包含。它包括所包含类型中声明的字段和方法。

class Person {
    string name;

    function init(string name) {
        self.name = name;
    }

    function getName() returns string {
        return self.name;
    }
}

class Employee {
    // Includes `Person`.
    // Therefore, `Employee` will also have the string field `name`
    // and will have to initialize it.
    // `Employee` will also have to implement the `getName` method.
    *Person; 
    // Additional field.
    string department;

    function init(string name, string department) {
        // `self.name` can be used as if the field was defined explicitly in `Employee`.
        self.name = name;
        self.department = department;
    }

    function getName() returns string {
        return self.name.trim();
    }
}

在这种特殊情况下，

RequestInterceptor

使用包含在

RequestInterceptor

模块中定义的

ballerina/http

不同对象类型。这使得

RequestInterceptor

成为 `http:RequestInterceptor.

的子类型。

另请参阅，

https://ballerina.io/learn/advanced-general- Purpose-language-features/#object-type-inclusion,

https://ballerina.io/learn/advanced-general- Purpose-language-features/#distinct-object-types