structure

1. memberwise initializer

　　1.1 不需要default values和intializer

///-------------------------- structures --------------------------///// only structures automatically generate a memberwise initializer// don't need default values and initializerstruct StructA {    let propertyA: Int    let propertyB: Double}//------------------ memberwise initializer ----------------//// the memberwise initializer works welllet a = StructA(propertyA: 1, propertyB: 1.0)

　　1.2 使用memberwise initializer注意参数的顺序，memberwise initializer的参数列表是自动镜像存储属性列表的，举例：

// the memberwise initializer doesn't work// the automatic memberwise initializer argument list's order mirrors that of the stored property listlet b = StructA(propertyB: 1.0, propertyA: 1)

　　1.3 如果属性已经有default value，则

struct StructA {    let propertyA: Int = 1    let propertyB: Double}let aa = StructA(propertyB: 1.0)

　　此时是不能 let aa = StructA(propertyA: 1, propertyB: 1.0) 的

 

　　如果想要，可以这么做，如下

2. 等价的 initializer

//equivalent initializerextension StructA {    init(propertyB: Double) {        self.propertyB = propertyB    }}// works welllet ab = StructA(propertyA: 1, propertyB: 1.0)

3. 添加default value

//-------------------------- custom initializer --------------------------//init(propertyA: Int = 1, propertyB: Double = 1.0) {    // 处理初始值}