CoreData (Database Upgrade) version migration-ios app upgrade installation

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If the iOS App is using CoreData and has database updates on the previous version (new tables, fields, and so on), the migration of the CoreData database will be done when the installer is overwritten, as follows:

1. Select your Mydata.xcdatamodeld file, select menu Editor->add Model Version, such as name: Mydata2.xcdatamodel

2. Set the current version

Select Superior Mydata.xcdatamodeld, select the current template as Mydata2 in the versioned Core Data model in Inspector

3. Modify the new data Model MYDATA2, add fields and tables to the new file

4. Delete the original class file and regenerate the following class.

In the Appdelegate

The first explanation : my "Coredata_new.xcdatamodeld"--- The entity model has been migrated from Model.xcdatamodeld to Model2.xcdatamodeld, and now I want to move to Model3.xcdatamodeld

Before you begin the operation

Here's how:

First step: Select the Zhongyuan version operation

Step Two: Check the add Model Version ... , there will be

Note: You will see that the new entity model file you created will be created based on your previous version. If there are many versions in front of you, choose which one you'd like to build on, choose the default one, or you'll have to lose the data if you choose an earlier version.

Step three: Click Finish will now be the new entity model Model3.xcdatamodeld, the data will be the same as the original

Fourth step: You can now do your data object operation, the specific data is not operational here

Fifth step: Now we choose the migrated version, go to the first interface, click on the model version, there will be your previous version, select you modify the new version of the data can be

Sixth step: After the selection, such as effect

Seventh Step: Code operation now

1,options system default options is nil, click to go API discovery is a dictionary, so we need to create a Dictionary object

I refine the point: Go into the API and then commad+f in the search bar to enter Autom

2, select the Always enter key to find as

Eighth step: code such as

The Nineth step: According to modify the code can be completed, run successfully.

Other additions,

Several classes used in the CoreData.
(1) Nsmanagedobjectmodel (managed object model)
Equivalent to an entity, but it contains relationships between entities
(2) Nsmanagedobjectcontext (Managed Object context)
Manipulating the actual content
Role: Insert Data query Update delete
(3) Nspersistentstorecoordinator (persistent storage assistant)
A connector equivalent to a database
(4) Nsfetchrequest (Request to get data)
Equivalent to a query statement
(5) Nspredicate (equivalent to query criteria)
(6) Nsentitydescription (solid structure)
(7) A package with a suffix named. Xcdatamodel
The. xcdatamodel file inside, edited with the Data Model Editor
Compiled for. MOMD or. Mom files, which is why there is no such thing in the file, and our program uses this thing without error.

Note: CoreData is an object-relational database, the biggest disadvantage is the thread relationship, can be stored in binary, database, XML format, can have version migration, this is better than SQL, SQL is database storage, object type database

"Coredata_new.xcdatamodeld"---entity model files
SQL gives the string, CoreData to the URL

/**COREDTA steps
* 1 Creating file Model files
* 2 Adding entities
* 3 Creating entity classes
* 4 Build context, parallel data model, generate database
*
Note: CoreData is an object-relational database, the biggest disadvantage is the thread relationship, can be stored in binary, database, XML format, can have version migration, this is better than SQL, SQL is database storage, object type database

"Coredata_new.xcdatamodeld"---entity model files
SQL gives the string, CoreData to the URL
*/

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Note: This is a personal custom operation, for reference only, if there are errors, please leave a message to indicate.

CoreData (Database Upgrade) version migration-ios app upgrade installation