@4djs/client 中文文档教程

Question

@4djs/client

4D 基础

How to use

Create a client

// Import the Client contructor from the module
const { Client } = require('@4djs/client');

// Create a client instance
const c = new m.Client(
  'http://localhost/rest', {
    user: 'admin',
    pass: 'admin'
  },
  { ctx: { req, res } },
);

// Get the catalog from client
const { ds } = await c.getCatalog();

Querying a table

的 NodeJS 连接器假设我们有一个目录，其中包含一个名为 Employee 的 DataClass。

运行此查询：

const collection = await ds.Employee.query('firstname == :1', 'Employee');

查找名字为 Employee 的员工。

Requests chaining

NodeJS 客户端允许请求链接。 例如，如果您运行此请求：

const array = await ds.Employee
  .query('firstname == :1', 'Employee')
  .orderBy('firstname asc')
  .skip(20).limit(5)
  .toArray('ID, firstname, lastname, company.name');

它将：

• Sort the result in ascending order by firstname
• Skip 20 entities
• Limit the result to 5 entities
• Converts the result to an array
• Selects the specified attributes

为了优化性能，客户端将在客户端 (NodeJS) 中准备请求，并且只向 4D 发送一个请求。

Create entity

创建实体非常简单：

const entity = new ds.Employee({ firstname: 'Employee' });
await entity.save();

execute 4D methods

运行 DataClass 方法：

const result = await ds.Employee.dataclassMethod('param');

这就是我们如何执行 entity method

const entity = await ds.Employee.find('ID = :1', 10108, {
  $attributes: 'ID',
});
const result = await entity.getFullName();

在上面的例子中：

• We retrieve an employee having the ID 10108 and we select only its ID attribute
• We execute the entity method named getFullName

working with the related Entity/Entities

const entity = await ds.Employee.find('ID = :1', 10108);
const employer = entity.employer;
await employer.refresh();

在上面的例子中：

• We retrieve an employee having the ID 10108 and we select only its ID attribute
• We get the related entity/entities attribute (we get an instance of Employee / EmployeeCollection)
• We load the related entity/entities from database

Compiling the typescript code

npm i # Will install the NodeJS dependencies
npm run build # Will transpile the code into javascript code

另一个选项是运行这个命令

npm run dev

这个命令将观察 typescript 的变化，然后将代码转换为 javascript