Coredata lightweight migration experience

 

 

Coredata has a small amount of related information on the Internet, most of which are basic usage. So I found the official documents of apple for further study.

Share your experiences. If coredata is used, you must understand coredata migration. Otherwise, the app version may encounter persistent coredata errors due to the change in the core data model schema,ProgramCrash.

Lightweight migration can be used to migrate data to the new model in the following situations.

Nsdictionary * Options = [ Nsdictionary Dictionarywithobjectsandkeys :[ Nsnumber Numberwithbool : Yes ], Nsmigratepersistentstoresautomaticallyoption ,[ Nsnumber Numberwithbool : Yes ], Nsinfermappingmodelautomaticallyoption , Nil ];

_ Persistentstorecoordinator= [[NspersistentstorecoordinatorAlloc]Initwithmanagedobjectmodel:[SelfManagedobjectmodel];

If(! [_ PersistentstorecoordinatorAddpersistentstorewithtype:NssqlitestoretypeConfiguration:NilURL: StoreurlOptions: OptionsError: & Error])

// OthersCode

-------------- Several situations are summarized as follows --------------------

1, simple addition of a new attribute. (add an attribute to an entity)

2. Removal of an attribute. (delete an attribute for an entity)

3, a non-optional attribute becoming optional.

4, an optional attribute becoming non-optional,And defining a default value.

5,Renaming an entity or property.

 

• Adding relationships and changing the type of relationship

  • You can add a new relationship or delete an existing relationship.

  • Renaming a relationship (by using a renaming identifier, just like an attribute)

  • Changing a relationship from a to-one to a to-random, or a non-ordered to-random to ordered (and visa-versa)

• Changing the entity hierarchy

• You can add, remove, rename entities

• You can create a new parent or child entity and move properties up and down the entity hierarchy

• You can move entities out of a hierarchy.

 

<Note>YouCannot, However, merge entity Hierarchies; if two existing entities do not share a common parent in the source, they cannot share a common parent in the destination. In this case, lightweight migration cannot be used.

Official documentation:

Https://developer.apple.com/library/ios/#documentation/Cocoa/Conceptual/CoreDataVersioning/Articles/vmLightweightMigration.html#//apple_ref/doc/uid/TP40004399-CH4-SW1

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