RLMMigration

@interface RLMMigration : NSObject

RLMMigration is the object passed into a user defined RLMMigrationBlock when updating the version of an RLMRealm instance.

This object provides access to the RLMSchema current to this migration.

Properties

  • Get the old RLMSchema for the migration. This is the schema which describes the RLMRealm before the migration is applied.

    Declaration

    Objective‑C

    @property (readonly, nonatomic) RLMSchema *_Nonnull oldSchema;
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  • Get the new RLMSchema for the migration. This is the schema which describes the RLMRealm after applying a migration.

    Declaration

    Objective‑C

    @property (readonly, nonatomic) RLMSchema *_Nonnull newSchema;
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Altering Objects during a Migration

  • Enumerates objects of a given type in this Realm, providing both the old and new versions of each object. Objects properties can be accessed using keyed subscripting.

    Warning

    All objects returned are of a type specific to the current migration and should not be casted to className. Instead you should access them as RLMObjects and use keyed subscripting to access properties.

    Declaration

    Objective‑C

    - (void)enumerateObjects:(nonnull NSString *)className
                   block:(nonnull RLMObjectMigrationBlock)block;

    Parameters

    className

    The name of the RLMObject class to enumerate.
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  • Create an RLMObject of type className in the Realm being migrated.

    Declaration

    Objective‑C

    - (nonnull RLMObject *)createObject:(nonnull NSString *)className
                          withValue:(nonnull id)value;

    Parameters

    className

    The name of the RLMObject class to create.
    value

    The value used to populate the created object. This can be any key/value coding compliant object, or a JSON object such as those returned from the methods in NSJSONSerialization, or an NSArray with one object for each persisted property. An exception will be thrown if any required properties are not present and no default is set.
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  • Delete an object from a Realm during a migration. This can be called within enumerateObjects:block:.

    Declaration

    Objective‑C

    - (void)deleteObject:(nonnull RLMObject *)object;

    Parameters

    object

    Object to be deleted from the Realm being migrated.
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  • Deletes the data for the class with the given name. This deletes all objects of the given class, and if the RLMObject subclass no longer exists in your program, cleans up any remaining metadata for the class in the Realm file.

    Declaration

    Objective‑C

    - (BOOL)deleteDataForClassName:(nonnull NSString *)name;

    Parameters

    name

    The name of the RLMObject class to delete.

    Return Value

    whether there was any data to delete.

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  • Rename property of the given class from oldName to newName.

    Declaration

    Objective‑C

    - (void)renamePropertyForClass:(nonnull NSString *)className
                       oldName:(nonnull NSString *)oldName
                       newName:(nonnull NSString *)newName;

    Parameters

    className

    Class for which the property is to be renamed. Must be present in both the old and new Realm schemas.
    oldName

    Old name for the property to be renamed. Must not be present in the new Realm.
    newName

    New name for the property to be renamed. Must not be present in the old Realm.
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