swift语言点评十八-异常与错误

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swift语言点评十八-异常与错误

1.错误类型与枚举的结合 enum VendingMachineError: Error { case invalidSelection case insufficientFunds(coinsNeeded: Int) case outOfStock } throw VendingMachineError.insufficientFunds(coinsNeeded: 5) 2.异常捕获与栈展开 Error handling in Swift resembles exception handlin…

swift语言点评十九-类型转化与检查

1.oc比较: -(BOOL) isKindOfClass: classObj判断是否是这个类或者这个类的子类的实例 -(BOOL) isMemberOfClass: classObj 判断是否是这个类的实例 2.is 类型检查 Use the type check operator (is) to check whether an instance is of a certain subclass type. 3. (as? or as!) 类型转化 Use the conditional f…

swift语言点评十四-继承

Overriding A subclass can provide its own custom implementation of an instance method, type method, instance property, type property, or subscript that it would otherwise inherit from a superclass. This is known as overriding. Overriding by accident…

swift语言点评十-Value and Reference Types

结论:value是拷贝,Reference是引用 Value and Reference Types Types in Swift fall into one of two categories: first, “value types”, where each instance keeps a unique copy of its data, usually defined as a struct, enum, or tuple. The second, “reference types”,…

swift语言点评十六-Initialization && Deinitialization

initial value:必须初始化.不影响观察者 Classes and structures must set all of their stored properties to an appropriate initial value by the time an instance of that class or structure is created. Stored properties cannot be left in an indeterminate state. You c…

swift语言点评十五-$0

import UIKitimport XCPlayground class ViewController: UIViewController { func action() { print("Bing!") } override func viewDidLoad() { super.viewDidLoad() view.backgroundColor = .whiteColor() let mySwitch : UISwitch = { view.addSubview($0) Cent…

swift语言点评十二-Subscripts

Classes, structures, and enumerations can define subscripts, which are shortcuts for accessing the member elements of a collection, list, or sequence. 下标的形式和函数相同,并且set和get合一 subscript(row: Int, column: Int) -> Double 比较: In addition to simple propert…