前言
入坑 wcdb 有两个月了，整体来说还是很不错的，具体优点可以参考文档说明，由于官方明确说明不支持 SQL 只好自己写一个扩展支持一下了
转自农民伯伯： http://over140.cnblogs.com
正文
一、功能实现
fork 一份源码然后把下面代码加入源码（有些类限制了访问作用域）
SelectSQL.swift
import Foundation
extension Database {
public func prepareSelectSQL(on propertyConvertibleList: [PropertyConvertible], sql: String, values: [ColumnEncodableBase] = []) throws -> SelectSQL {
return try SelectSQL(with: self, on: propertyConvertibleList, sql: sql, values: values)
}
}
public final class SelectSQL {
private final var core: Core
final var optionalRecyclableHandleStatement: RecyclableHandleStatement?
final var statement: StatementSelectSQL
private let keys: [CodingTableKeyBase]
private let values: [ColumnEncodableBase]
private lazy var decoder = TableDecoder(keys, on: optionalRecyclableHandleStatement!)
init(with core: Core, on propertyConvertibleList: [PropertyConvertible], sql: String, values: [ColumnEncodableBase]) throws {
//TODO: Use generic to check all coding table keys conform to same root type
keys = propertyConvertibleList.asCodingTableKeys()
self.statement = StatementSelectSQL(sql: sql)
self.core = core
self.values = values
}
private func bindValues() throws {
guard values.count > 0 else {
return
}
let handleStatement = try lazyHandleStatement()
for idx in 0..<values.count {
handleStatement.bind(values[idx].archivedFundamentalValue(), toIndex: idx + 1)
}
}
deinit {
try? finalize()
}
/// Get all selected objects according to the `CodingTableKey`.
///
/// - Returns: Table decodable objects according to the `CodingTableKey`
/// - Throws: `Error`
public func allObjects() throws -> [Any] {
let rootType = keys[0].rootType as? TableDecodableBase.Type
assert(rootType != nil, "\(keys[0].rootType) must conform to TableDecodable protocol.")
var objects: [Any] = []
try bindValues()
while try next() {
objects.append(try rootType!.init(from: decoder))
}
return objects
}
/// Get all selected objects.
///
/// - Parameter type: Type of table decodable object
/// - Returns: Table decodable objects.
/// - Throws: `Error`
public func allObjects<Object: TableDecodable>(of type: Object.Type = Object.self) throws -> [Object] {
assert(keys is [Object.CodingKeys], "Properties must belong to \(Object.self).CodingKeys.")
var objects: [Object] = []
try bindValues()
while try next() {
objects.append(try Object.init(from: decoder))
}
return objects
}
final func finalize() throws {
if let recyclableHandleStatement = optionalRecyclableHandleStatement {
try recyclableHandleStatement.raw.finalize()
optionalRecyclableHandleStatement = nil
}
}
final func lazyHandleStatement() throws -> HandleStatement {
if optionalRecyclableHandleStatement == nil {
optionalRecyclableHandleStatement = try core.prepare(statement)
}
return optionalRecyclableHandleStatement!.raw
}
//Since `next()` may throw errors, it can't conform to `Sequence` protocol to fit a `for in` loop.
@discardableResult
public final func next() throws -> Bool {
do {
return try lazyHandleStatement().step()
} catch let error {
try? finalize()
throw error
}
}
}
extension SelectSQL: CoreRepresentable {
/// The tag of the related database.
public final var tag: Tag? {
return core.tag
}
/// The path of the related database.
public final var path: String {
return core.path
}
}StatementSelectSQL.swift
import Foundation
public final class StatementSelectSQL: Statement {
public private(set) var description: String = ""
public var statementType: StatementType {
return .select
}
public init(sql: String) {
self.description = sql
}
}UpdateSQL.swift
import Foundation
extension Database {
public func prepareUpdateSQL(sql: String) throws -> UpdateSQL {
return try UpdateSQL(with: self, sql: sql)
}
}
/// The chain call for updating
public final class UpdateSQL {
private var core: Core
private let statement: StatementUpdateSQL
/// The number of changed rows in the most recent call.
/// It should be called after executing successfully
public var changes: Int?
init(with core: Core, sql: String) throws {
self.core = core
self.statement = StatementUpdateSQL(sql: sql)
}
/// Execute the update chain call with row.
///
/// - Parameter row: Column encodable row
/// - Throws: `Error`
public func execute(with row: [ColumnEncodableBase?] = []) throws {
let recyclableHandleStatement: RecyclableHandleStatement = try core.prepare(statement)
let handleStatement = recyclableHandleStatement.raw
for (index, value) in row.enumerated() {
let bindingIndex = index + 1
handleStatement.bind(value?.archivedFundamentalValue(), toIndex: bindingIndex)
}
try handleStatement.step()
changes = handleStatement.changes
}
}
extension UpdateSQL: CoreRepresentable {
/// The tag of the related database.
public var tag: Tag? {
return core.tag
}
/// The path of the related database.
public var path: String {
return core.path
}
}StatementUpdateSQL.swift
import Foundation
public final class StatementUpdateSQL: Statement {
public private(set) var description: String = ""
public var statementType: StatementType {
return .update
}
public init(sql: String) {
self.description = sql
}
}二、使用 SQL 查询或更新数据
2.1 查询
1 | database.prepareSelectSQL(User.Properties.Id, "SELECT id FROM users where id = ?", values: ["1"]) |
需要特别注意的是如果返回 Codable 数据，SELECT 字段的顺序必须要和 CodingKeys 里的顺序一致，否则数据会填充乱，但是用 WINQ 不会有这个问题。
2.2 更新
1 2 | let updateSQL = try database.prepareUpdateSQL(sql: "UPDATE conversations SET last_message_id = (select id from messages where conversation_id = ? order by created_at DESC limit 1) WHERE conversation_id = ?")try updateSQL.execute(with: [conversationId, conversationId]) |
结束
目前用了一段时间没有发现什么问题，除了前面那个注意顺序问题，WINQ 就是拼 SQL 语句搞不懂官方为啥不直接支持一个，就算能支持所有 SQL 改起来也很麻烦，而且代码量很多。
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每日一句
More dreams are lost to self-doubt than to failure.
因自我怀疑而失去的梦想比因失败而失去的更多。
因自我怀疑而失去的梦想比因失败而失去的更多。
