Promise

The Promise object is used for asynchronous computations. A Promise represents a value which may be available now, or in the future, or never.

In Slimane, There is no Promise library in codes. So need to install Thrush which is a light weight Promise Implementation without threading.

It also has similar apis to the ES promise. For more detail, visit https://github.com/noppoMan/Thrush

Package.swift

import PackageDescription

let package = Package(
    name: "MyApp",
    dependencies: [
        .Package(url: "https://github.com/noppoMan/Thrush.git", majorVersion: 0, minor: 2),
    ]
)

Example

Here is an asynchronously database manipulate example with Promise

import Thrush

extension DB {
    func execute(sql: String) -> Promise<FooResult> {
        return Promise<FooResult> { resolve, reject in
            let onThread = { ctx in
                do
                    ctx.storage["result"] = try blockingSqlQuery(sql)
                } catch {
                    ctx.storage["error"] = error
                }
            }

            let onFinish = { ctx in
                if let error = ctx.storage["error"] as? Error {
                    reject(error)
                    return
                }

                resolve(ctx.storage["result"] as! FooResult)
            }

            Process.qwork(onThread: onThread, onFinish: onFinish)
        }
    }
}

let db = DB(host: "localhost")

db.execute("insert into users (id, name) values (1, 'jack')").then {
    print($0)
}
.`catch` {
    print($0)
}
.finally {
    print("Done")
}