YapDatabaseView

@interface YapDatabaseView : YapDatabaseExtension

YapDatabaseView is an abstract class that implements the underlying logic for several subclasses:

  • YapDatabaseAutoView
  • YapDatabaseManualView
  • YapDatabaseMultiView

  • The versionTag assists you in updating the view configuration.

    For example, if you need to change the groupingBlock or sortingBlock, then simply pass a different versionTag during the init method, and the view will automatically update itself.

    If you want to keep things simple, you can use something like @1, representing version 1 of my groupingBlock & sortingBlock.

    For more advanced applications, you may also include within the versionTag string:

    • localization information (if you’re using localized sorting routines)
    • configuration information (if your sorting routine is based on some in-app configuration)

    For example, if you’re sorting strings using a localized string compare method, then embedding the localization information into your versionTag means the view will automatically re-populate itself (re-sort) if the user launches the app in a different language than last time.

    NSString *localeIdentifier = [[NSLocale currentLocale] localeIdentifier]; NSString *versionTag = [NSString stringWithFormat:@1-%@, localeIdentifier];

    The groupingBlock/sortingBlock/versionTag can me changed after the view has been created. See YapDatabaseViewTransaction(ReadWrite).

    Note:

    • [YapDatabaseView versionTag] = versionTag of most recent commit
    • [YapDatabaseViewTransaction versionTag] = versionTag of this commit

    Declaration

    Objective-C

    @property (readonly, copy, nonatomic) NSString *_Nonnull versionTag;

    Swift

    var versionTag: String { get }

  • The options allow you to specify things like creating an in-memory-only view (non persistent).

    Declaration

    Objective-C

    @property (readonly, copy, nonatomic) YapDatabaseViewOptions *_Nonnull options;

    Swift

    @NSCopying var options: YapDatabaseViewOptions { get }

  • Allows you to fetch the versionTag from a view that was registered during the last app launch.

    For example, let’s say you have a view that sorts contacts. And you support 2 different sort options:

    • First, Last
    • Last, First

    To support this, you use 2 different versionTags:

    • First,Last
    • Last,First

    And you want to ensure that when you first register the view (during app launch), you choose the same block & versionTag from a previous app launch (if possible). This prevents the view from enumerating the database & re-populating itself during registration if the versionTag is different from last time.

    So you can use this method to fetch the previous versionTag.

    Declaration

    Objective-C

    + (nullable NSString *)
    previousVersionTagForRegisteredViewName:(nonnull NSString *)name
                            withTransaction:
                                (nonnull YapDatabaseReadTransaction *)
                                    transaction;

    Swift

    class func previousVersionTag(forRegisteredViewName name: String, with transaction: YapDatabaseReadTransaction) -> String?