Stanford University Open Class: iOS8 Development first Lesson: iOS8 Overview study notes

Last Update:2015-06-24 Source: Internet

Author: User

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1. All objects, class. instances of the class are in the heap 2. Let represents a constant, and once you set an initial value for it, it cannot be changed within this method. 3. If you put a \ () in the string, you can put an expression in Parentheses. Swift evaluates the expression, and then converts the value into a string, which is then embedded in it, such asprintln("digit = \ (digit)") Print out is digit = Optional ("9") 4. There are only two types of Optional: 1. Not set: indicates that the value has not been set by anyone, or someone intentionally set it to an undefined state2. There are values: 5. Swift is not a weak type. it is a very, very strong type of language. but Swift has a very powerful feature called type deduction letdigit = Sender.Currenttitle! 6. The next exclamation mark is to unpack the optiona and get the real property, but if the property is empty it crashesthe value must be assigned at initialization timevarishavetext:Bool=false7. If you do not unpack it directly for operation, such as: display . text = digit + Display .text The compiler will not know its type Error. All code class Viewcontroller:Uiviewcontroller { @IBOutlet Weak var display: UILabel!var userisinthemiddleoftypingannumber: Bool = false;@IBAction func numberbuttonclick (sender:UIButton) { let digit = Sender. currenttitle! ifuserisinthemiddleoftypingannumber {display. text = digit +display. text!}Else {display. text = digit userisinthemiddleoftypingannumber =true}println ("digit = \(digit)")}} Stanford University Open Class: iOS8 Development first Lesson: iOS8 Overview study notes

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Stanford University Open Class: iOS8 Development first Lesson: iOS8 Overview study notes

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