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C＃概念(C# CONCEPTS)

什么是方法链接？(What is Method Chaining?)

It’s used to link multiple methods calls into a single compound statement. Method Chaining requires that every method return an interface that supports chaining. It may take some time to get used to because even setters in a Fluent world should have a return interface, which goes against what we’re used to in traditional data patterns.

它用于将多个方法调用链接到单个复合语句中。 方法链接要求每个方法都返回一个支持链接的接口。 可能要花一些时间才能习惯，因为即使在Fluent的世界中，设置员也应该具有返回接口，这与我们在传统数据模式中惯用的接口相反。

Example

例

//Method Chainingvar students = StudentDetailsUsingMethodChaining.Select().WithCourse("Course 1").Fetch;

什么是连词？ (What is Conjunctions?)

Conjunctions words like AND, OR, NOR, FOR, and NOT are required when combining multiple paths into one statement.

将多个路径组合到一条语句中时，需要使用AND ， OR ， NOR ， FOR和NOT之类的连接词。

Example

例

//Conjunctionsvar conjectionStudents = StudentDetailsUsingConjuction.Select().WithCourse("Course 1").And.Exclude("student 1").Fetch;

Let’s take the example of a student who has applied for different courses like Course 1, Course 2, and so on.

让我们以一个已经申请了不同课程(例如课程1，课程2等)的学生为例。

要求 (Requirements)

How to fetch the list of students with course 1?

如何获取课程1的学生名单？How to fetch the list of students with course 2?

如何获取课程2的学生名单？

应用方法链接 (Apply Method Chaining)

Our main goal is to achieve LINQ like method chaining as shown below as Select, WithCourse & Fetch.

我们的主要目标是实现类似于LINQ的方法链接，如下所示，如Select, WithCourse & Fetch.

//Method Chainingvar students = StudentDetailsUsingMethodChaining.Select().WithCourse("Course 1").Fetch;

Please find below the examples of entity class & their relevant Interface.

请在下面找到实体类及其相关接口的示例。

学生实体 (Student Entity)

An entity that consists of the student name and course object.

由学生姓名和课程对象组成的实体。

public class StudentModel{ public string Name { get; set; } public CourseModel Courses { get; set; }}

课程实体 (Courses Entity)

An entity that consists of course name and its weightage.

由课程名称及其权重组成的实体。

public class CourseModel{ public string CourseName { get; set; } public string Weightage { get; set; }}

学生界面 (IStudent Interface)

Fluent Interface with a property that returns ICourses.

流利的接口，具有返回ICourses的属性。

public interface IStudent{ ICourses Courses { get; }}

课程接口 (ICourses Interface)

Fluent Interface with method WithCourses, which filters a list of courses by course name & returns IStudent interface.

具有方法WithCourses的Fluent接口，该方法按课程名称过滤课程列表并返回IStudent接口。

public interface ICourses{ IStudent WithCourse(string courseName);}

For populating data, the below method is used.

要填充数据，请使用以下方法。

private List<CourseModel> courses = new List<CourseModel>();private List<StudentModel> students = new List<StudentModel>();public void PrepareData(){ var course1 = new CourseModel() { CourseName = "Course 1", Weightage = "5" };var course2 = new CourseModel() { CourseName = "Course 2", Weightage = "4" };var course3 = new CourseModel() { CourseName = "Course 3", Weightage = "3" }; courses.Add(course1); courses.Add(course2); courses.Add(course3);students.Add(new StudentModel() { Name = "student 1", Courses = course1 } ); students.Add(new StudentModel() { Name = "student 2", Courses = course1 } ); students.Add(new StudentModel() { Name = "student 3", Courses = course1 } ); students.Add(new StudentModel() { Name = "student 4", Courses = course2 } ); students.Add(new StudentModel() { Name = "student 5", Courses = course1 } ); students.Add(new StudentModel() { Name = "student 6", Courses = course3 } );}

iStudent接口实现 (IStudent interface implementation)

public class Student : IStudent{ public Student() { }private IEnumerable<StudentModel> vals; public Student(IEnumerable<StudentModel> values) { vals = values; }public List<StudentModel> Fetch => vals.ToList(); public ICourses Courses => new Courses();}

ICourses界面实现 (ICourses interface implementation)

public class Courses : ICourses{ private List<CourseModel> courses = new List<CourseModel>(); private List<StudentModel> students = new List<StudentModel>();public Courses() { PrepareData(); } //Perpare Data is shown above public IStudent WithCourse(string courseName) { return new Student(students.Where(x => x.Courses.CourseName.Equals(courseName))); }}

封装Student类的初始化 (Encapsulate the Student class initialization)

The below class contains a static method “Select()” which in turn creates a Student class object and return Courses associated with it.

下面的类包含一个静态方法“ Select()” ，该方法又创建了一个Student类对象并返回与之关联的Courses。

public class StudentDetailsUsingMethodChaining{public static FluentApiExample.MethodChaining.ICourses Select() { return new FluentApiExample.MethodChaining.Student().Courses; }}

测试方法链接 (Test Method Chaining)

The “StudentDetailsUsingMethodChaining” class contains a static method called “Select()” which returns an “ICourses” interface.

“ StudentDetailsUsingMethodChaining”类包含一个名为“ Select()”的静态方法，该方法返回“ ICourses”接口。

Now “ICourses” interface contains a method “WithCourse,” which filters the students based upon course name and returns an “IStudent” interface.

现在，“ ICourses”界面包含“ WithCourse”方法，该方法根据课程名称过滤学生并返回“ IStudent”界面。

The “IStudent” interface contains a method “Fetch,” which returns the filtered students by course name.

“ IStudent”界面包含“ Fetch”方法，该方法按课程名称返回过滤的学生。

var students = StudentDetailsUsingMethodChaining.Select().WithCourse("Course 1").Fetch;foreach (var student in students){ Console.WriteLine($@"Students of Course 1 : {student.Name}");}//Output//Students of Course 1 : student 1//Students of Course 1 : student 2//Students of Course 1 : student 3//Students of Course 1 : student 5

Learn to apply conjunctions to fetch a list of students opted for Course 1 excluding student 1.

学习应用连接词来获取选择了课程1的学生(学生1除外)的列表。

要求 (Requirements)

How to fetch a list of students with course 1 excluding student 1?

如何获取课程1(学生1除外)的学生列表？How to fetch a list of students with course 1, including student 6?

如何获取课程1(包括学生6)的学生列表？

应用连词 (Apply Conjunctions)

Our main goal is to achieve LINQ like method chaining as shown below as Select, WithCourse, Exclude & Fetch.

我们的主要目标是实现类似于LINQ的方法链接，如下所示，如Select, WithCourse, Exclude & Fetch.

//Conjunctionsvar conjectionStudents = StudentDetailsUsingConjuction.Select().WithCourse("Course 1").And.Exclude("student 1").Fetch;

ICourses界面修改如下所示 (ICourses interface modified as shown below)

Two new methods are introduced, namely, Include & Exclude.

引入了两种新方法，即Include ＆ Exclude 。

public interface ICourses{ IStudent WithCourse(string courseName); IStudent Include(string studentName); IStudent Exclude(string studentName);}

修改了IStudent的界面，如下所示。 (IStudent interface modified, as shown below.)

New conjunction is added named “AND.”

添加了名为“ AND”的新连接。

public interface IStudent{ ICourses Courses { get; } ICourses And { get; } List<StudentModel> Fetch { get; }}

ICourses interface implementation is updated with new methods.

使用新方法更新了ICourses接口的实现。

//....public Courses(IEnumerable<StudentModel> students){ this.students = students.ToList();}public IStudent Include(string studentName){ return new Student( students.Where(x => x.Name.Equals(studentName)) .ToList() );}public IStudent Exclude(string studentName){ return new Student( students.Where(x => !x.Name.Equals(studentName)) .ToList() );}//....

测试连词 (Test Conjunctions)

The “StudentDetailsUsingMethodChaining” class contains a static method called “Select()” which returns an “ICourses” interface.

“ StudentDetailsUsingMethodChaining”类包含一个名为“ Select()”的静态方法，该方法返回“ ICourses”接口。

Now “ICourses” interface contains a method “WithCourse,” which filters the students based upon course name and returns an “IStudent” interface.

现在，“ ICourses”界面包含“ WithCourse”方法，该方法根据课程名称过滤学生并返回“ IStudent”界面。

The “AND” conjunction passed the IStudent Interface to Courses, which contains a new method “Exclude,” which filters the existing collection by student name & returns the “IStudent” interface.

“ AND”联合将IStudent接口传递给课程，其中包含新方法“ Exclude” ，该方法按学生姓名过滤现有馆藏并返回“ IStudent”接口。

The “IStudent” interface contains a method “Fetch,” which returns the filtered students by course name.

“ IStudent”界面包含“ Fetch”方法，该方法按课程名称返回过滤的学生。

//Conjunctionsvar conjectionStudents = StudentDetailsUsingConjuction.Select().WithCourse("Course 1").And.Exclude("student 1").Fetch;foreach (var student in conjectionStudents){ Console.WriteLine($@"Students of Course 1 : {student.Name}");}//Output//Students of Course 1 : student 2//Students of Course 1 : student 3//Students of Course 1 : student 5

Github示例 (Github Sample)

The below consists of implementations of method chaining and conjunctions differentiated with a namespace.

以下内容由方法链接和以命名空间区分的连接的实现组成。

感谢您的阅读。 (Thank you for reading.)

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翻译自: https://medium.com/@singhsukhpinder/fluent-interface-design-pattern-17eb43ee0a4b

手机界面设计模式