MagicalRecord入门教程 

分类： ios开发2014-03-13 23:53 9535人阅读 评论(2) 收藏 举报

目录(?)[+]

Magical Record是什么

在Cocoa中存在一种技术叫Core Data，用来对数据进行持久化，类似于Java世界中的Hibernate。在新建Cocoa Application/iOS Application的向导中，有一个选项是要不要使用Core Data，当启用以后你会发现在AppDelegate.m中添加了大量与Core Data相关的代码，但是你对大部分代码不知所以然。

Magical Record的出现在一定程度上缓解了这个问题，降低了Core Data的使用门槛。

Magical Record借用了Ruby on Rails中的Active Record模式，使得你可以非常容易的添加、查找、删除数据。Google了一下，没有发现中文相关教程，遂把自己的试用过程记录下来，写成此篇文章。

安装

1. 新建一个项目，注意在向导中不要勾选Core Data。
2. 下载Magical Record，并把MagicalRecord目录拖拽到工程中，记得勾选copy items into group folder。
3. 为项目添加CoreData FrameWork。(点击工程根节点，然后依次Targets > Build Phases > Link Binary With Libraries > + > CoreData.framework > Add)。
4. 添加Magical Record的头文件到*-Prefix.pch：           #import "CoreData+MagicalRecord.h"

创建模型文件

下面创建一个名为Person的模型，有age、firstname、lastname三个字段。

1. 创建一个名为Model的模型文件。 (File > New File… > Core Data > Data Model)
2. 点击左下角的Add Entity，更改Entity的名字为Person。
3. 为Entity添加三个Attribute：age(Integer16)、firstname(string)、lastname(string)。
4. 点击Editor > Create NSManagedObject Subclass… > Create创建模型文件对应的类。

使用Magical Record

初始化Magical Record

首先在AppDelegate.m中添加以下代码对Magical Record进行初始化：

1. -(void)applicationDidFinishLaunching:(NSNotification*)aNotification
2. {
3. [MagicalRecord setupCoreDataStackWithStoreNamed:@"MyDatabase.sqlite"];
4. // ...
5. return YES;
6. }
8. -(void)applicationWillTerminate:(NSNotification*)aNotification
9. {
10. [MagicalRecord cleanUp];
11. }

是否比Core Data默认的初始化简洁多了呢？

查询记录

使用Person的MR_findAll、MR_findAllSortedBy、MR_findByAttribute等方法可以查询Person：

1. //查找数据库中的所有Person。
2. NSArray*persons=[Person MR_findAll];
4. //查找所有的Person并按照first name排序。
5. NSArray*personsSorted=[Person MR_findAllSortedBy:@"firstname" ascending:YES];
7. //查找所有age属性为25的Person记录。
8. NSArray*personsAgeEuqals25=[Person MR_findByAttribute:@"age" withValue:[NSNumber numberWithInt:25]];
10. //查找数据库中的第一条记录
11. Person*person=[Person MR_findFirst];

</pre><h2 style="margin:10px 0px 0px; padding:0px; border-width:0px 0px 1px; border-bottom-style:solid; border-bottom-color:rgb(221,221,221); font-size:1.285714286rem; vertical-align:baseline; clear:both; line-height:1.6; font-weight:300; color:rgb(102,102,102); font-family:HelveticaNeue-Light,'Helvetica Neue Light','Helvetica Neue',Helvetica,Arial,'Lucida Grande',sans-serif; text-align:justify; background-color:rgb(238,238,238)"><a target=_blank target="_blank" name="t6" style="color:rgb(51,102,153)"></a><span style="margin:0px; padding:0px; border:0px; font-size:18px; vertical-align:baseline; background-color:rgb(255,255,255)">添加记录</span></h2><p style="margin-top:10px; margin-bottom:1.714285714rem; padding-top:0px; padding-bottom:0px; border:0px; vertical-align:baseline; line-height:28px; color:rgb(102,102,102); font-family:HelveticaNeue-Light,'Helvetica Neue Light','Helvetica Neue',Helvetica,Arial,'Lucida Grande',sans-serif; text-align:justify; background-color:rgb(238,238,238)"><span style="margin:0px; padding:0px; border:0px; vertical-align:baseline; background-color:rgb(255,255,255)">使用Person的MR_createEntity方法可以方便的创建一个Person，需要使用[[NSManagedObjectContext MR_defaultContext] MR_save]来进行保存哦：</span></p><p style="margin-top:10px; margin-bottom:1.714285714rem; padding-top:0px; padding-bottom:0px; border:0px; vertical-align:baseline; line-height:28px; color:rgb(102,102,102); font-family:HelveticaNeue-Light,'Helvetica Neue Light','Helvetica Neue',Helvetica,Arial,'Lucida Grande',sans-serif; text-align:justify; background-color:rgb(238,238,238)"><span style="margin:0px; padding:0px; border:0px; vertical-align:baseline; background-color:rgb(255,255,255)"></span></p><ol class="linenums" style="font-family:Consolas,Monaco,'Lucida Console',monospace; font-size:14px; white-space:pre-wrap; background-color:rgb(51,51,51); margin:0px; padding:0px 0px 0px 27px; border:0px; vertical-align:baseline; list-style-position:outside; line-height:1.714285714; color:rgb(174,174,174)"><li value="1" class="L0" style="margin:0px; padding:0px; border:0px; vertical-align:baseline; line-height:16px; list-style:decimal"><span style="margin:0px; padding:0px; border:0px; vertical-align:baseline; background-color:rgb(255,255,255)"><code style="margin:0px; padding:0px; border:none; font-size:0.9em; vertical-align:baseline; font-family:Menlo,Monaco,'Andale Mono','lucida console','Courier New',monospace; line-height:2; display:block"><span class="typ" style="margin:0px; padding:0px; border:0px; vertical-align:baseline; color:rgb(152,251,152)">Person</span><span class="pln" style="margin:0px; padding:0px; border:0px; vertical-align:baseline; color:rgb(255,255,255)"></span><span class="pun" style="margin:0px; padding:0px; border:0px; vertical-align:baseline; color:rgb(255,255,255)">*</span><span class="pln" style="margin:0px; padding:0px; border:0px; vertical-align:baseline; color:rgb(255,255,255)">person</span><span class="pun" style="margin:0px; padding:0px; border:0px; vertical-align:baseline; color:rgb(255,255,255)">=</span><span class="pln" style="margin:0px; padding:0px; border:0px; vertical-align:baseline; color:rgb(255,255,255)"></span><span class="pun" style="margin:0px; padding:0px; border:0px; vertical-align:baseline; color:rgb(255,255,255)">[</span><span class="typ" style="margin:0px; padding:0px; border:0px; vertical-align:baseline; color:rgb(152,251,152)">Person</span><span class="pln" style="margin:0px; padding:0px; border:0px; vertical-align:baseline; color:rgb(255,255,255)"> MR_createEntity</span><span class="pun" style="margin:0px; padding:0px; border:0px; vertical-align:baseline; color:rgb(255,255,255)">];</span></code></span></li><li class="L1" style="margin:0px; padding:0px; border:0px; vertical-align:baseline; line-height:16px; list-style:decimal"><span style="margin:0px; padding:0px; border:0px; vertical-align:baseline; background-color:rgb(255,255,255)"><code style="margin:0px; padding:0px; border:none; font-size:0.9em; vertical-align:baseline; font-family:Menlo,Monaco,'Andale Mono','lucida console','Courier New',monospace; line-height:2; display:block"><span class="pln" style="margin:0px; padding:0px; border:0px; vertical-align:baseline; color:rgb(255,255,255)">person</span><span class="pun" style="margin:0px; padding:0px; border:0px; vertical-align:baseline; color:rgb(255,255,255)">.</span><span class="pln" style="margin:0px; padding:0px; border:0px; vertical-align:baseline; color:rgb(255,255,255)">firstname</span><span class="pun" style="margin:0px; padding:0px; border:0px; vertical-align:baseline; color:rgb(255,255,255)">=</span><span class="pln" style="margin:0px; padding:0px; border:0px; vertical-align:baseline; color:rgb(255,255,255)"></span><span class="pun" style="margin:0px; padding:0px; border:0px; vertical-align:baseline; color:rgb(255,255,255)">@</span><span class="str" style="margin:0px; padding:0px; border:0px; vertical-align:baseline; color:rgb(255,160,160)">"Frank"</span><span class="pun" style="margin:0px; padding:0px; border:0px; vertical-align:baseline; color:rgb(255,255,255)">;</span></code></span></li><li class="L2" style="margin:0px; padding:0px; border:0px; vertical-align:baseline; line-height:16px; list-style:decimal"><span style="margin:0px; padding:0px; border:0px; vertical-align:baseline; background-color:rgb(255,255,255)"><code style="margin:0px; padding:0px; border:none; font-size:0.9em; vertical-align:baseline; font-family:Menlo,Monaco,'Andale Mono','lucida console','Courier New',monospace; line-height:2; display:block"><span class="pln" style="margin:0px; padding:0px; border:0px; vertical-align:baseline; color:rgb(255,255,255)">person</span><span class="pun" style="margin:0px; padding:0px; border:0px; vertical-align:baseline; color:rgb(255,255,255)">.</span><span class="pln" style="margin:0px; padding:0px; border:0px; vertical-align:baseline; color:rgb(255,255,255)">lastname</span><span class="pun" style="margin:0px; padding:0px; border:0px; vertical-align:baseline; color:rgb(255,255,255)">=</span><span class="pln" style="margin:0px; padding:0px; border:0px; vertical-align:baseline; color:rgb(255,255,255)"></span><span class="pun" style="margin:0px; padding:0px; border:0px; vertical-align:baseline; color:rgb(255,255,255)">@</span><span class="str" style="margin:0px; padding:0px; border:0px; vertical-align:baseline; color:rgb(255,160,160)">"Zhang"</span><span class="pun" style="margin:0px; padding:0px; border:0px; vertical-align:baseline; color:rgb(255,255,255)">;</span></code></span></li><li class="L3" style="margin:0px; padding:0px; border:0px; vertical-align:baseline; line-height:16px; list-style:decimal"><span style="margin:0px; padding:0px; border:0px; vertical-align:baseline; background-color:rgb(255,255,255)"><code style="margin:0px; padding:0px; border:none; font-size:0.9em; vertical-align:baseline; font-family:Menlo,Monaco,'Andale Mono','lucida console','Courier New',monospace; line-height:2; display:block"><span class="pln" style="margin:0px; padding:0px; border:0px; vertical-align:baseline; color:rgb(255,255,255)">person</span><span class="pun" style="margin:0px; padding:0px; border:0px; vertical-align:baseline; color:rgb(255,255,255)">.</span><span class="pln" style="margin:0px; padding:0px; border:0px; vertical-align:baseline; color:rgb(255,255,255)">age</span><span class="pun" style="margin:0px; padding:0px; border:0px; vertical-align:baseline; color:rgb(255,255,255)">=</span><span class="pln" style="margin:0px; padding:0px; border:0px; vertical-align:baseline; color:rgb(255,255,255)"></span><span class="pun" style="margin:0px; padding:0px; border:0px; vertical-align:baseline; color:rgb(255,255,255)">@</span><span class="lit" style="margin:0px; padding:0px; border:0px; vertical-align:baseline; color:rgb(205,92,92)">26</span><span class="pun" style="margin:0px; padding:0px; border:0px; vertical-align:baseline; color:rgb(255,255,255)">;</span><span class="com" style="margin:0px; padding:0px; border:0px; vertical-align:baseline; color:rgb(135,206,235)">//此处使用了LLVM的新特性，XCode 4.4可用</span></code></span></li><li class="L4" style="margin:0px; padding:0px; border:0px; vertical-align:baseline; line-height:16px; list-style:decimal"><span style="margin:0px; padding:0px; border:0px; vertical-align:baseline; background-color:rgb(255,255,255)"><code style="margin:0px; padding:0px; border:none; font-size:0.9em; vertical-align:baseline; font-family:Menlo,Monaco,'Andale Mono','lucida console','Courier New',monospace; line-height:2; display:block"><span class="pun" style="margin:0px; padding:0px; border:0px; vertical-align:baseline; color:rgb(255,255,255)">[[</span><span class="typ" style="margin:0px; padding:0px; border:0px; vertical-align:baseline; color:rgb(152,251,152)">NSManagedObjectContext</span><span class="pln" style="margin:0px; padding:0px; border:0px; vertical-align:baseline; color:rgb(255,255,255)"> MR_defaultContext</span><span class="pun" style="margin:0px; padding:0px; border:0px; vertical-align:baseline; color:rgb(255,255,255)">]</span><span class="pln" style="margin:0px; padding:0px; border:0px; vertical-align:baseline; color:rgb(255,255,255)"> MR_save</span><span class="pun" style="margin:0px; padding:0px; border:0px; vertical-align:baseline; color:rgb(255,255,255)">];</span></code></span></li></ol><p></p><pre class="wp-code-highlight prettyprint linenums:1 prettyprinted" name="code" style="white-space: pre-wrap; word-wrap: normal; margin-top: 6px; margin-bottom: 6px; padding: 2px 7px; border: 1px solid rgb(237, 237, 237); vertical-align: baseline; color: rgb(102, 102, 102); font-family: Consolas, Monaco, 'Lucida Console', monospace; line-height: 16px; overflow: auto; background-color: rgb(51, 51, 51); width: 858.46875px;">

更新记录

直接对数据库中查找到的Person进行赋值，然后使用NSManagedObjectContext保存即可更新Person：

1. Person*person=...;//此处略
2. person.lastname=object;
3. [[NSManagedObjectContext MR_defaultContext] MR_save];

删除记录

使用Person的MR_deleteEntity可以方便的删除Person，模式和添加更新一致：

1. Person*person=...;//此处略
2. [person MR_deleteEntity];
3. [[NSManagedObjectContext MR_defaultContext] MR_save];

</pre><p></p><pre class="wp-code-highlight prettyprint linenums:1 prettyprinted" name="code" style="white-space:pre-wrap; word-wrap:normal; margin-top:6px; margin-bottom:6px; padding:2px 7px; border:1px solid rgb(237,237,237); vertical-align:baseline; color:rgb(102,102,102); font-family:Consolas,Monaco,'Lucida Console',monospace; line-height:16px; overflow:auto; background-color:rgb(51,51,51); width:858.46875px">

小技巧

启动时MR_mergedObjectModelFromMainBundle方法报错

Core Data的模型有版本的概念，有可能在你Magical Record第一次初始化完成以后，你又更改了模型文件，导致Core Data去合并模型报错。解决办法很简单，点击菜单中的Project->Clean即可。

项目使用ARC后，编译Magical Record不通过

点击项目 -> Build Phases -> Compile Sources中, 双击报错的class文件, 编辑Compiler Flags加入 -fno-objc-arc。

不想使用MR_前缀

只需要在*-Prefix.pch文件中添加一句#define MR_SHORTHAND即可，注意这句要在#import “CoreData+MagicalRecord.h”之前。

参考链接：

Magical Record: how to make programming with Core Data pleasant

注：这篇文章中的MagicalRecordHelpers、MRCoreDataAction都已经不在新版本的Magical Record中存在，都已经更改为MagicalRecord。

纪录一下链接http://blog.csdn.net/kuizhang1/article/details/21200367