需要自定义 Sequelize Postgres 数据类型的工作示例

Question

我想在 Sequelize 中使用 Postgres 中的自定义类型。我已经根据 Sequelize 文档中的示例编写了代码，除了调用我在 Sequelize 或其他地方找不到的函数（“继承”）。但是，使用 sequelize.define 创建具有此自定义类型属性的模型会在 Sequelize 中引发异常。我的代码中是否有突出的错误？还是有另一个很好的例子或教程来实现自定义数据类型？此外，文档示例中显示的“继承”函数是怎么回事——文档是否遗漏了导入/要求，或者该调用是否错误？

我关注的文档在这里：http://docs.sequelizejs.com/manual/data-types.html#extending-datatypes

Postgres 中定义的类型：

CREATE TYPE public.measurement AS
(
    unit text,
    value double precision
);

我在 NodeJS 中的测试代码：

const Sequelize = require('sequelize');

let dataTypes = Sequelize.DataTypes;

// Create class for custom datatype
class MEASUREMENT extends dataTypes.ABSTRACT {
    toSql() {
        console.log('MEASUREMENT toSql');
        return 'MEASUREMENT';
    }
    static parse(value) {
        console.log('MEASUREMENT parse value=', value);
        return value;
    }
};

// Set key
MEASUREMENT.prototype.key = 'MEASUREMENT';
MEASUREMENT.key = MEASUREMENT.prototype.key;

// Add to DataTypes
dataTypes.MEASUREMENT = MEASUREMENT;

// Add to Sequelize
Sequelize.MEASUREMENT = Sequelize.Utils.classToInvokable(MEASUREMENT);

let pgTypes = dataTypes.postgres;

// Map dialects
dataTypes.MEASUREMENT.types.postgres = ['MEASUREMENT']

pgTypes.MEASUREMENT = function MEASUREMENT() {
    if (!(this instanceof pgTypes.MEASUREMENT)) return new pgTypes.MEASUREMENT();
    DataTypes.MEASUREMENT.apply(this, arguments);
}

// inherits(pgTypes.MEASUREMENT, dataTypes.MEASUREMENT);
// Node throws a parse error. This is in the example in the Sequelize docs, however.

pgTypes.MEASUREMENT.parse = dataTypes.MEASUREMENT.parse;


// ------------------------------

const sequelize = new Sequelize('test', 'test', 'test', {
    host: 'localhost',
    dialect: 'postgres'
});

const Thing = sequelize.define('thing', {
    name: Sequelize.STRING,
    weight: Sequelize.MEASUREMENT
});

运行时调用堆栈：

C:\Workspaces\nebula\server\node_modules\sequelize\lib\dialects\abstract\connection-manager.js:48
        if (dataType.types[this.dialectName]) {                                                                         
                          ^                                                                                             

TypeError: Cannot read property 'postgres' of undefined                                                                 
    at _.each.dataType (C:\Workspaces\nebula\server\node_modules\sequelize\lib\dialects\abstract\connection-manager.js:48:27)                                                                                                                   
    at C:\Workspaces\nebula\server\node_modules\lodash\lodash.js:4911:15                                                
    at baseForOwn (C:\Workspaces\nebula\server\node_modules\lodash\lodash.js:2996:24)                                   
    at C:\Workspaces\nebula\server\node_modules\lodash\lodash.js:4880:18                                                
    at Function.forEach (C:\Workspaces\nebula\server\node_modules\lodash\lodash.js:9344:14)                             
    at ConnectionManager.refreshTypeParser (C:\Workspaces\nebula\server\node_modules\sequelize\lib\dialects\abstract\connection-manager.js:46:7)                                                                                                
    at new ConnectionManager (C:\Workspaces\nebula\server\node_modules\sequelize\lib\dialects\postgres\connection-manager.js:23:10)                                                                                                             
    at new PostgresDialect (C:\Workspaces\nebula\server\node_modules\sequelize\lib\dialects\postgres\index.js:14:30)    
    at new Sequelize (C:\Workspaces\nebula\server\node_modules\sequelize\lib\sequelize.js:320:20)                       
    at Object.<anonymous> (C:\Workspaces\nebula\server\testsequelizecustom.js:58:19)                                    
    at Module._compile (internal/modules/cjs/loader.js:689:30)                                                          
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:700:10)                                            
    at Module.load (internal/modules/cjs/loader.js:599:32)                                                              
    at tryModuleLoad (internal/modules/cjs/loader.js:538:12)                                                            
    at Function.Module._load (internal/modules/cjs/loader.js:530:3)                                                     
    at Function.Module.runMain (internal/modules/cjs/loader.js:742:12)                                                  
    at startup (internal/bootstrap/node.js:279:19)                                                                      
    at bootstrapNodeJSCore (internal/bootstrap/node.js:752:3)                                                           

Answer 1

要修复错误，我们需要定义对象dataType.types 上的属性postgres。

就在你已经拥有的那一行之下：

pgTypes.MEASUREMENT.parse = dataTypes.MEASUREMENT.parse;

添加以下行，错误应该会消失：

pgTypes.MEASUREMENT.types = {postgres:[‘MEASUREMENT’]};

您可能还需要添加这一行，以处理相关错误（见下文）。

dataTypes.postgres.MEASUREMENT.key = ‘MEASUREMENT’;

相关错误：

[...]/node_modules/sequelize/lib/dialects/postgres/connection-manager.js:36
if (dataType.key.toLowerCase() === 'range') {
                         ^
    
TypeError: Cannot read property 'toLowerCase' of undefined