AssociationAggregate

public struct AssociationAggregate<RowDecoder>

An AssociationAggregate is able to compute aggregated values from a population of associated records.

For example:

struct Author: TableRecord {
    static let books = hasMany(Book.self)
}

let bookCount = Author.books.count // AssociationAggregate<Author>

Association aggregates can be used in the annotated(with:) and having(_:) request methods:

let request = Author.annotated(with: bookCount)
let request = Author.having(bookCount >= 10)

The RowDecoder generic type helps the compiler prevent incorrect use of aggregates:

// Won't compile because Fruit is not Author.
let request = Fruit.annotated(with: bookCount)

  • Returns an aggregate that is selected in a column with the given name.

    For example:

    let aggregate = Author.books.count.aliased("numberOfBooks")
let request = Author.annotated(with: aggregate)
if let row = try Row.fetchOne(db, request) {
    let numberOfBooks: Int = row["numberOfBooks"]
}

    Declaration

    Swift

    @available(*, deprecated, renamed: "forKey(_:﹚")
public func aliased(_ name: String) -> AssociationAggregate<RowDecoder>
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  • Returns an aggregate that is selected in a column with the given name.

    For example:

    let aggregate = Author.books.count.forKey("numberOfBooks")
let request = Author.annotated(with: aggregate)
if let row = try Row.fetchOne(db, request) {
    let numberOfBooks: Int = row["numberOfBooks"]
}

    Declaration

    Swift

    public func forKey(_ key: String) -> AssociationAggregate<RowDecoder>
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  • Returns an aggregate that is selected in a column named like the given coding key.

    For example:

    struct AuthorInfo: Decodable, FetchableRecord {
    var author: Author
    var numberOfBooks: Int

    static func fetchAll(_ db: Database) throws -> [AuthorInfo] {
        let aggregate = Author.books.count.aliased(CodingKeys.numberOfBooks)
        let request = Author.annotated(with: aggregate)
        return try AuthorInfo.fetchAll(db, request)
    }
}

    Declaration

    Swift

    @available(*, deprecated, renamed: "forKey(_:﹚")
public func aliased(_ key: CodingKey) -> AssociationAggregate<RowDecoder>
    Show on GitHub

  • Returns an aggregate that is selected in a column named like the given coding key.

    For example:

    struct AuthorInfo: Decodable, FetchableRecord {
    var author: Author
    var numberOfBooks: Int

    static func fetchAll(_ db: Database) throws -> [AuthorInfo] {
        let aggregate = Author.books.count.forKey(CodingKeys.numberOfBooks)
        let request = Author.annotated(with: aggregate)
        return try AuthorInfo.fetchAll(db, request)
    }
}

    Declaration

    Swift

    public func forKey(_ key: CodingKey) -> AssociationAggregate<RowDecoder>
    Show on GitHub