Core Data 教程(2): 如何预载/导入已有的数据

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前端之家收集整理的这篇文章主要介绍了Core Data 教程(2): 如何预载/导入已有的数据，前端之家小编觉得挺不错的，现在分享给大家，也给大家做个参考。

这是系列教程的第二部分，有助于你加快掌握基本的Core Data内容。

在系列教程一中，我们为对象建立了可视化数据模型，运行了快速肮脏测试并勾在一个表视图(table view)中来显示。而在这个教程，我们将讨论如何把已有的数据导入或者预先载入到Core Data里面，这样我们的应用开始时会有一些好的默认数据。

在系列教程的最后部分，我们将讨论如何使用NSFetchedResultsController来优化应用，降低内存开销和提升响应时间。

Preloading / Importing Existing Data

预载/导入已有数据

我们要如何在Core Data中预先载入数据呢？流行的解决方案有两种：

  • 启动时从外部源填入Core Data。对此，注意到数据库还没有导入，应用可以启动时从外部来源(例如sqlite数据库或是XML文件)读取数据。
  • 在sqlite数据库中预先填充。对此我们可以Core Data在模型基础上建立数据库结构，然后使用工具来填入数据库。这类工具可以是基于Core Data API的Mac或者iPhone应用，或是一些直接填入sqlite数据库的程序。一旦数据库填好了，只需将其包含到应用里面作为默认数据库，在不存在已有的数据库情况下。

我们将会采用第二种方式，因为它更简单更有效。为了填充数据库，我们只需稍微扩展一下已有的Python脚本。

注意到为什么用Python脚本而不是用基于Core Data API的工具来来导入数据，是因为我们现在有点走底层的样子，将来可能会容易损坏…但是对于本教程我认为第一，由于我们刚刚接触了sqlite，这样对学习的经验巩固更好，而且对事情的进展看的更加清楚；第二，更简单！

所以，让我们拿出工程中产生的sqlite数据库的拷贝。找出相关文件的最简单的方法就是在程序委托(application delegate)中persistentStoreCoordinator函数里面storeUrl一行下方设置一个断点。你可以通过检测storeUrl变量的内容来获取sqlite数据库备份文件的完整路径。找到它并拷到你的Python脚本目录。

一旦你找到数据库，使用sqlite3来简单看看数据库的模样:

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sqlite3 FailedBanksCD.sqlite
sqlite3> . schema
CREATE TABLE ZFailedBANKDETAILS ( Z_PK INTEGER PRIMARY KEY ,Z_ENT INTEGER sql plain" style="margin-top:0px!important; margin-right:0px!important; margin-bottom:0px!important; margin-left:0px!important; padding-top:0px!important; padding-right:0px!important; padding-bottom:0px!important; padding-left:0px!important; border-top-width:0px!important; border-right-width:0px!important; border-bottom-width:0px!important; border-left-width:0px!important; border-style:initial; border-color:initial; outline-width:0px!important; outline-style:initial!important; outline-color:initial!important; font-size:1em!important; vertical-align:baseline!important; background-color:initial!important; border-style:initial!important; border-color:initial!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; overflow-x:visible!important; overflow-y:visible!important; position:static!important; right:auto!important; text-align:left!important; top:auto!important; width:auto!important; font-family:Consolas,
@H_301_152@ Z_OPT sql keyword" style="margin-top:0px!important; margin-right:0px!important; margin-bottom:0px!important; margin-left:0px!important; padding-top:0px!important; padding-right:0px!important; padding-bottom:0px!important; padding-left:0px!important; border-top-width:0px!important; border-right-width:0px!important; border-bottom-width:0px!important; border-left-width:0px!important; border-style:initial; border-color:initial; outline-width:0px!important; outline-style:initial!important; outline-color:initial!important; font-size:1em!important; vertical-align:baseline!important; background-color:initial!important; border-style:initial!important; border-color:initial!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; overflow-x:visible!important; overflow-y:visible!important; position:static!important; right:auto!important; text-align:left!important; top:auto!important; width:auto!important; font-family:Consolas,ZZIP sql keyword" style="margin-top:0px!important; margin-right:0px!important; margin-bottom:0px!important; margin-left:0px!important; padding-top:0px!important; padding-right:0px!important; padding-bottom:0px!important; padding-left:0px!important; border-top-width:0px!important; border-right-width:0px!important; border-bottom-width:0px!important; border-left-width:0px!important; border-style:initial; border-color:initial; outline-width:0px!important; outline-style:initial!important; outline-color:initial!important; font-size:1em!important; vertical-align:baseline!important; background-color:initial!important; border-style:initial!important; border-color:initial!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; overflow-x:visible!important; overflow-y:visible!important; position:static!important; right:auto!important; text-align:left!important; top:auto!important; width:auto!important; font-family:Consolas,ZINFO sql keyword" style="margin-top:0px!important; margin-right:0px!important; margin-bottom:0px!important; margin-left:0px!important; padding-top:0px!important; padding-right:0px!important; padding-bottom:0px!important; padding-left:0px!important; border-top-width:0px!important; border-right-width:0px!important; border-bottom-width:0px!important; border-left-width:0px!important; border-style:initial; border-color:initial; outline-width:0px!important; outline-style:initial!important; outline-color:initial!important; font-size:1em!important; vertical-align:baseline!important; background-color:initial!important; border-style:initial!important; border-color:initial!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; overflow-x:visible!important; overflow-y:visible!important; position:static!important; right:auto!important; text-align:left!important; top:auto!important; width:auto!important; font-family:Consolas,ZUPDATEDDATE TIMESTAMP sql plain" style="margin-top:0px!important; margin-right:0px!important; margin-bottom:0px!important; margin-left:0px!important; padding-top:0px!important; padding-right:0px!important; padding-bottom:0px!important; padding-left:0px!important; border-top-width:0px!important; border-right-width:0px!important; border-bottom-width:0px!important; border-left-width:0px!important; border-style:initial; border-color:initial; outline-width:0px!important; outline-style:initial!important; outline-color:initial!important; font-size:1em!important; vertical-align:baseline!important; background-color:initial!important; border-style:initial!important; border-color:initial!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; overflow-x:visible!important; overflow-y:visible!important; position:static!important; right:auto!important; text-align:left!important; top:auto!important; width:auto!important; font-family:Consolas,
ZCLOSEDATE );
ZFailedBANKINFO ( Z_PK sql keyword" style="margin-top:0px!important; margin-right:0px!important; margin-bottom:0px!important; margin-left:0px!important; padding-top:0px!important; padding-right:0px!important; padding-bottom:0px!important; padding-left:0px!important; border-top-width:0px!important; border-right-width:0px!important; border-bottom-width:0px!important; border-left-width:0px!important; border-style:initial; border-color:initial; outline-width:0px!important; outline-style:initial!important; outline-color:initial!important; font-size:1em!important; vertical-align:baseline!important; background-color:initial!important; border-style:initial!important; border-color:initial!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; overflow-x:visible!important; overflow-y:visible!important; position:static!important; right:auto!important; text-align:left!important; top:auto!important; width:auto!important; font-family:Consolas,
sql keyword" style="margin-top:0px!important; margin-right:0px!important; margin-bottom:0px!important; margin-left:0px!important; padding-top:0px!important; padding-right:0px!important; padding-bottom:0px!important; padding-left:0px!important; border-top-width:0px!important; border-right-width:0px!important; border-bottom-width:0px!important; border-left-width:0px!important; border-style:initial; border-color:initial; outline-width:0px!important; outline-style:initial!important; outline-color:initial!important; font-size:1em!important; vertical-align:baseline!important; background-color:initial!important; border-style:initial!important; border-color:initial!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; overflow-x:visible!important; overflow-y:visible!important; position:static!important; right:auto!important; text-align:left!important; top:auto!important; width:auto!important; font-family:Consolas,ZNAME VARCHAR sql plain" style="margin-top:0px!important; margin-right:0px!important; margin-bottom:0px!important; margin-left:0px!important; padding-top:0px!important; padding-right:0px!important; padding-bottom:0px!important; padding-left:0px!important; border-top-width:0px!important; border-right-width:0px!important; border-bottom-width:0px!important; border-left-width:0px!important; border-style:initial; border-color:initial; outline-width:0px!important; outline-style:initial!important; outline-color:initial!important; font-size:1em!important; vertical-align:baseline!important; background-color:initial!important; border-style:initial!important; border-color:initial!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; overflow-x:visible!important; overflow-y:visible!important; position:static!important; right:auto!important; text-align:left!important; top:auto!important; width:auto!important; font-family:Consolas,ZSTATE sql keyword" style="margin-top:0px!important; margin-right:0px!important; margin-bottom:0px!important; margin-left:0px!important; padding-top:0px!important; padding-right:0px!important; padding-bottom:0px!important; padding-left:0px!important; border-top-width:0px!important; border-right-width:0px!important; border-bottom-width:0px!important; border-left-width:0px!important; border-style:initial; border-color:initial; outline-width:0px!important; outline-style:initial!important; outline-color:initial!important; font-size:1em!important; vertical-align:baseline!important; background-color:initial!important; border-style:initial!important; border-color:initial!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; overflow-x:visible!important; overflow-y:visible!important; position:static!important; right:auto!important; text-align:left!important; top:auto!important; width:auto!important; font-family:Consolas,
ZCITY );
Z_MetaDATA (Z_VERSION sql keyword" style="margin-top:0px!important; margin-right:0px!important; margin-bottom:0px!important; margin-left:0px!important; padding-top:0px!important; padding-right:0px!important; padding-bottom:0px!important; padding-left:0px!important; border-top-width:0px!important; border-right-width:0px!important; border-bottom-width:0px!important; border-left-width:0px!important; border-style:initial; border-color:initial; outline-width:0px!important; outline-style:initial!important; outline-color:initial!important; font-size:1em!important; vertical-align:baseline!important; background-color:initial!important; border-style:initial!important; border-color:initial!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; overflow-x:visible!important; overflow-y:visible!important; position:static!important; right:auto!important; text-align:left!important; top:auto!important; width:auto!important; font-family:Consolas,
Z_UUID (255),Z_PLIST BLOB);
Z_PRIMARYKEY (Z_ENT sql keyword" style="margin-top:0px!important; margin-right:0px!important; margin-bottom:0px!important; margin-left:0px!important; padding-top:0px!important; padding-right:0px!important; padding-bottom:0px!important; padding-left:0px!important; border-top-width:0px!important; border-right-width:0px!important; border-bottom-width:0px!important; border-left-width:0px!important; border-style:initial; border-color:initial; outline-width:0px!important; outline-style:initial!important; outline-color:initial!important; font-size:1em!important; vertical-align:baseline!important; background-color:initial!important; border-style:initial!important; border-color:initial!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; overflow-x:visible!important; overflow-y:visible!important; position:static!important; right:auto!important; text-align:left!important; top:auto!important; width:auto!important; font-family:Consolas,Z_NAME sql keyword" style="margin-top:0px!important; margin-right:0px!important; margin-bottom:0px!important; margin-left:0px!important; padding-top:0px!important; padding-right:0px!important; padding-bottom:0px!important; padding-left:0px!important; border-top-width:0px!important; border-right-width:0px!important; border-bottom-width:0px!important; border-left-width:0px!important; border-style:initial; border-color:initial; outline-width:0px!important; outline-style:initial!important; outline-color:initial!important; font-size:1em!important; vertical-align:baseline!important; background-color:initial!important; border-style:initial!important; border-color:initial!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; overflow-x:visible!important; overflow-y:visible!important; position:static!important; right:auto!important; text-align:left!important; top:auto!important; width:auto!important; font-family:Consolas,
@H_404_198@Z_SUPER sql keyword" style="margin-top:0px!important; margin-right:0px!important; margin-bottom:0px!important; margin-left:0px!important; padding-top:0px!important; padding-right:0px!important; padding-bottom:0px!important; padding-left:0px!important; border-top-width:0px!important; border-right-width:0px!important; border-bottom-width:0px!important; border-left-width:0px!important; border-style:initial; border-color:initial; outline-width:0px!important; outline-style:initial!important; outline-color:initial!important; font-size:1em!important; vertical-align:baseline!important; background-color:initial!important; border-style:initial!important; border-color:initial!important; bottom:auto!important; float:none!important; height:auto!important; left:auto!important; line-height:1.1em!important; overflow-x:visible!important; overflow-y:visible!important; position:static!important; right:auto!important; text-align:left!important; top:auto!important; width:auto!important; font-family:Consolas,Z_MAX );
INDEX ZFailedBANKDETAILS_ZINFO_INDEX ON ZFailedBANKDETAILS (ZINFO);
ZFailedBANKINFO_ZDETAILS_INDEX ZFailedBANKINFO (ZDETAILS);
sqlite> select * from ZFailedBANKINFO;
1|2|1|1|Test Bank|Testland|Testville
2|2|1|2|Test Bank|Testland|Testville
3|2|1|3|Test Bank|Testland|Testville
ZFailedBANKDETAILS;
1|1|1|12345|1|292794835.855615|292794835.679693
2|1|1|12345|2|292794875.943392|292794875.768675
3|1|1|12345|3|292795809.375025|292795809.215297
Z_PRIMARYKEY;
1|FailedBankDetails|0|3
2|FailedBankInfo|0|3

这里有段快速描述。Z_MetaDATA包含了一些关于Core Data需要实现的模型信息。Z_PRIMARYKEY包含了(在其他东西里面)各个实体所用到的最大key。

至于ZFailedBANKINFO跟ZFailedBANKDETAILS，这些是我们的主要数据表。Z_PK是各个表的唯一id，Z_ENT是他们的实体id(跟Z_PRIMARYKEY表中列出的一样)，最后那些是我们的普通字段。

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