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结构体

• 结构体基础

struct Location{
    let latitude: Double
    let longitude: Double
}

let appleHeadQuarterLocation: Location = Location(latitude: 37.3230, longitude: -122.0322)

struct Place {
    let location: Location
    var name: String
}

var appleHeadQuarter = Place(location: appleHeadQuarterLocation, name: "Apple")
appleHeadQuarter.location.latitude  // 37.323

• 结构体之构造函数

struct Location{
    let latitude: Double
    let longitude: Double
    var placeName: String?
    
    init(coordinateString: String) {
//        let preIndex = coordinateString.range(of: ",")!.lowerBound
//        let sufIndex = coordinateString.range(of: ",")!.upperBound
//        self.latitude = Double(coordinateString.prefix(upTo: preIndex)) ?? 0
//        self.longitude = Double(coordinateString.suffix(from: sufIndex)) ?? 0
        
        let commaIndex = coordinateString.index(of: ",")!
        self.latitude = Double(coordinateString[..<commaIndex]) ?? 0
        self.longitude = Double(coordinateString[coordinateString.index(after: commaIndex)..<coordinateString.endIndex]) ?? 0
    }
    
    init(latitude: Double, longitude: Double) {
        self.latitude = latitude
        self.longitude = longitude
    }
    
    init(latitude: Double, longitude: Double, placeName: String) {
        self.latitude = latitude
        self.longitude = longitude
        self.placeName = placeName
    }
}


let location = Location(coordinateString: "37.3230,-122.0322")
let location2 = Location(latitude: 37.3230, longitude: -122.0322)
let location3 = Location(latitude: 37.3220, longitude: -122.0322, placeName: "Apple Head Quarter")

• 结构体之可失败的构造函数

struct Location{
    let latitude: Double
    let longitude: Double
    var placeName: String?
    
    init?(coordinateString: String) {
        if let commaIndex = coordinateString.index(of: ","){
            self.latitude = Double(coordinateString[..<commaIndex]) ?? 0
            self.longitude = Double(coordinateString[coordinateString.index(after: commaIndex)..<coordinateString.endIndex]) ?? 0
        }else {
            return nil
        }
    }
    
}


let location = Location(coordinateString: "37.3230&-122.0322")  // nil

• 在结构体和枚举中定义方法

struct Location{
    let latitude: Double
    let longitude: Double
    var placeName: String?
    
    init?(coordinateString: String) {
        if let commaIndex = coordinateString.index(of: ","){
            self.latitude = Double(coordinateString[..<commaIndex]) ?? 0
            self.longitude = Double(coordinateString[coordinateString.index(after: commaIndex)..<coordinateString.endIndex]) ?? 0
        }else {
            return nil
        }
    }
    
    func printLocation() {
        print(self.latitude)
        print(self.longitude)
    }
}


let location = Location(coordinateString: "37.3230,-122.0322")
location?.printLocation()

• 结构体和枚举是值类型

struct Point {
    var x = 0
    var y = 0
}

var p1 = Point()
var p2 = p1

p1.x += 1
p1.x  // 1
p2.x  // 0

• 随处可见的结构体

// Array, Dictionary, Set 都是结构体
// Int, Float, Double, Bool, String 都是结构体