Swift的180個(gè)介紹
一、新增一個(gè)swapAt方法
-
for example（可以很方便的互換兩個(gè)元素）
var numbers = [1,2,3,4,5,6]
print(numbers) // [1,2,3,4,5,6]
numbers.swapAt(2, 5)
print(numbers) // [1, 2, 6, 4, 5, 3]
swap(&numbers[0], &numbers[1])
print(numbers) // [2, 1, 6, 4, 5, 3]
打印效果.png
二七问、SE-0148使用泛型下標(biāo)操作符
-
正常情況下
struct JSON {
private var data: [String: Any]
init(data: [String: Any]) {
self.data = data
}
subscript(key: String) -> Any? {
return data[key]
}
}
let json = JSON(data: [
"name": "MG明明",
"age": 43
])
let name: String? = json["name"] as? String // "MG明明"
let age: Int? = json["age"] as? Int // 43
-
修改泛型
struct JSON {
private var data: [String: Any]
init(data: [String: Any]) {
self.data = data
}
subscript <T>(key: String) -> T? {
return data[key] as? T
}
}
let json = JSON(data: [
"name": "MG明明",
"age": 43
])
let name: String? = json["name"] // "MG明明"
let age: Int? = json["age"] // 43
- 三师枣、#SE-0156 Subtype existential
protocol P {}
struct S : P {}
class C : P {}
class D { }
let t: AnyObject & P = S() // Compiler error: S is not of class type
let u: AnyObject & P = C() // Compiles successfully
let v: P & AnyObject = C() // Compiles successfully
let w: P & AnyObject = D() // Compiler error: class D does not conform to protocol P
protocol P {}
class C {}
class D : C { }
class E : C { }
class F : D, P { }
let t: C & D & P = F() // Okay: F is a subclass of D and conforms to P
let u: D & P = t // Okay: D & P is equivalent to C & D & P
let v: C & D & P = u // Okay: C & D & P is equivalent to D & P
let w: D & E & P // Compiler error: D is not a subclass of E or vice-versa
