QueryableSource

public protocol QueryableSource : AnyObject

Encapsulates containers which manages an internal NSManagedObjectContext, such as DataStacks and transactions, that can be used for querying values. CoreStore provides implementations for this protocol and should be used as a read-only abstraction.

  • Queries aggregate values as specified by the QueryClauses. Requires at least a Select clause, and optional Where, OrderBy, GroupBy, and Tweak clauses.

    A “query” differs from a “fetch” in that it only retrieves values already stored in the persistent store. As such, values from unsaved transactions or contexts will not be incorporated in the query result.

    Throws

    CoreStoreError.persistentStoreNotFound if the specified entity could not be found in any store’s schema.

    Declaration

    Swift

    func queryValue<O, U>(_ from: From<O>, _ selectClause: Select<O, U>, _ queryClauses: QueryClause...) throws -> U? where O : DynamicObject, U : QueryableAttributeType

    Parameters

    from

    a From clause indicating the entity type
    selectClause

    a Select<U> clause indicating the properties to fetch, and with the generic type indicating the return type.
    queryClauses

    a series of QueryClause instances for the query request. Accepts Where, OrderBy, GroupBy, and Tweak clauses.

    Return Value

    the result of the the query, or nil if no match was found. The type of the return value is specified by the generic type of the Select<U> parameter.

  • Queries aggregate values as specified by the QueryClauses. Requires at least a Select clause, and optional Where, OrderBy, GroupBy, and Tweak clauses.

    A “query” differs from a “fetch” in that it only retrieves values already stored in the persistent store. As such, values from unsaved transactions or contexts will not be incorporated in the query result.

    Throws

    CoreStoreError.persistentStoreNotFound if the specified entity could not be found in any store’s schema.

    Declaration

    Swift

    func queryValue<O, U>(_ from: From<O>, _ selectClause: Select<O, U>, _ queryClauses: [QueryClause]) throws -> U? where O : DynamicObject, U : QueryableAttributeType

    Parameters

    from

    a From clause indicating the entity type
    selectClause

    a Select<U> clause indicating the properties to fetch, and with the generic type indicating the return type.
    queryClauses

    a series of QueryClause instances for the query request. Accepts Where, OrderBy, GroupBy, and Tweak clauses.

    Return Value

    the result of the the query, or nil if no match was found. The type of the return value is specified by the generic type of the Select<U> parameter.

  • Queries a property value or aggregate as specified by the QueryChainableBuilderType built from a chain of clauses.

    A “query” differs from a “fetch” in that it only retrieves values already stored in the persistent store. As such, values from unsaved transactions or contexts will not be incorporated in the query result.

    let averageAdultAge = dataStack.queryValue(
    From<MyPersonEntity>()
        .select(Int.self, .average(\.age))
        .where(\.age > 18)
)

    Throws

    CoreStoreError.persistentStoreNotFound if the specified entity could not be found in any store’s schema.

    Declaration

    Swift

    func queryValue<B>(_ clauseChain: B) throws -> B.ResultType? where B : QueryChainableBuilderType, B.ResultType : QueryableAttributeType

    Parameters

    clauseChain

    a QueryChainableBuilderType indicating the property/aggregate to fetch and the series of queries for the request.

    Return Value

    the result of the the query as specified by the QueryChainableBuilderType, or nil if no match was found.

  • Queries a dictionary of attribute values as specified by the QueryClauses. Requires at least a Select clause, and optional Where, OrderBy, GroupBy, and Tweak clauses.

    A “query” differs from a “fetch” in that it only retrieves values already stored in the persistent store. As such, values from unsaved transactions or contexts will not be incorporated in the query result.

    Throws

    CoreStoreError.persistentStoreNotFound if the specified entity could not be found in any store’s schema.

    Declaration

    Swift

    func queryAttributes<O>(_ from: From<O>, _ selectClause: Select<O, NSDictionary>, _ queryClauses: QueryClause...) throws -> [[String : Any]] where O : DynamicObject

    Parameters

    from

    a From clause indicating the entity type
    selectClause

    a Select<U> clause indicating the properties to fetch, and with the generic type indicating the return type.
    queryClauses

    a series of QueryClause instances for the query request. Accepts Where, OrderBy, GroupBy, and Tweak clauses.

    Return Value

    the result of the the query. The type of the return value is specified by the generic type of the Select<U> parameter.

  • Queries a dictionary of attribute values as specified by the QueryClauses. Requires at least a Select clause, and optional Where, OrderBy, GroupBy, and Tweak clauses.

    A “query” differs from a “fetch” in that it only retrieves values already stored in the persistent store. As such, values from unsaved transactions or contexts will not be incorporated in the query result.

    Throws

    CoreStoreError.persistentStoreNotFound if the specified entity could not be found in any store’s schema.

    Declaration

    Swift

    func queryAttributes<O>(_ from: From<O>, _ selectClause: Select<O, NSDictionary>, _ queryClauses: [QueryClause]) throws -> [[String : Any]] where O : DynamicObject

    Parameters

    from

    a From clause indicating the entity type
    selectClause

    a Select<U> clause indicating the properties to fetch, and with the generic type indicating the return type.
    queryClauses

    a series of QueryClause instances for the query request. Accepts Where, OrderBy, GroupBy, and Tweak clauses.

    Return Value

    the result of the the query. The type of the return value is specified by the generic type of the Select<U> parameter.

  • Queries a dictionary of attribute values or as specified by the QueryChainableBuilderType built from a chain of clauses.

    A “query” differs from a “fetch” in that it only retrieves values already stored in the persistent store. As such, values from unsaved transactions or contexts will not be incorporated in the query result.

    let results = source.queryAttributes(
    From<MyPersonEntity>()
        .select(
            NSDictionary.self,
            .attribute(\.age, as: "age"),
            .count(\.age, as: "numberOfPeople")
        )
        .groupBy(\.age)
)
for dictionary in results! {
    let age = dictionary["age"] as! Int
    let count = dictionary["numberOfPeople"] as! Int
    print("There are \(count) people who are \(age) years old."
}

    Throws

    CoreStoreError.persistentStoreNotFound if the specified entity could not be found in any store’s schema.

    Declaration

    Swift

    func queryAttributes<B>(_ clauseChain: B) throws -> [[String : Any]] where B : QueryChainableBuilderType, B.ResultType == NSDictionary

    Parameters

    clauseChain

    a QueryChainableBuilderType indicating the properties to fetch and the series of queries for the request.

    Return Value

    the result of the the query as specified by the QueryChainableBuilderType

  • The internal NSManagedObjectContext managed by this QueryableSource. Using this context directly should typically be avoided, and is provided by CoreStore only for extremely specialized cases.

    Declaration

    Swift

    func unsafeContext() -> NSManagedObjectContext