如何获取核心数据中现有实体（表）的列表 [英] How to get list of existing entities(tables) in core data

问题描述

如何获取核心数据中特定模式（托管对象模型）的现有实体（表）列表。我刚刚开始实现核心数据概念，坚持这些要点，请帮助

How to get list of existing entities(tables) for a particular schema(Managed object model) in core data. I just started implementing core data concept and stuck with these points, please help

像：SELECT COUNT（*）FROM information_schema.tables WHERE table_schema ='dbName';

something like : SELECT COUNT(*) FROM information_schema.tables WHERE table_schema = 'dbName';

感谢

推荐答案

您应该通读 Apple的核心数据编程指南。要获得特定 NSManagedObjectModel 的实体，您可以使用下列其中一个（假设您有一个 NSManagedObjectModel 命名 objectModel ）：

You should read through Apple's Core Data Programming Guide. To get the entities for a particular NSManagedObjectModel, you would use one of the following (this assumes you have an NSManagedObjectModel named objectModel):

NSArray *myEntities = [objectModel entities];
// Array of all entities in the model

或

NSDictionary *myEntities = [objectModel entitiesByName];
// Dictionary of entities in the model, with the entity names as keys

请阅读 NSManagedObjectModel类参考。

看起来你是从SQL背景来的（像我一样）。 Core Data中有许多不同的概念 - 有时候，一旦理解它们，有时需要比可能使用的简单SQL语句更多的工作。我认为重要的是，没有SQL行李来处理核心数据，如果你是第一次学习如何使用数据库，这将有助于避免挫折。

It appears you're coming from a SQL background (as I was). There are a number of concepts in Core Data that are different - sometimes for the better, once you understand them, sometimes requiring more work than a simple SQL statement you may be used to. I think it's important to approach Core Data without SQL "baggage" and treat it as if you're learning how to use a database for the first time - this will help avoid frustration.

这篇关于如何获取核心数据中现有实体（表）的列表的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！