Play Transfer swift--Study notes (continuous update)

Recently in learning iOS development, take notes down!

1. Constants and variables

   • Let-constants Constants

let maxNum =32

• Var-variables variable

varindex0

• Declare multiple variables at the same time

var x=0.0,y=0.0,z=0.0

• Types can be inferred, or they can be explicitly declared

var0//这里是一个整形var str:String"123"  //这是一个字符串

• Basic type
  int (integral type)
  Double,float (floating point)
  String (String)
  BOOL (Boolean type)

• Number Type
  Decimal
  Binary 0b101
  Octal 0o5
  Hex 0x5

• Can be counted with science

let0.012let1.2e-2  //值为0.012

• Numbers can be separated by underscores

let1_000_000let1_0000_0000

• Type conversions

let1let1.3232let num_c:Double = num_b + Double(num_a)  //此处需要强制转换

1. Boolean type and if statement

   • The IF can be followed without parentheses, but curly braces are required.

   • The condition cannot be of another type, it must be a Boolean type

trueif isTrue{    println("is true") }else{    println("is false")}

1. Tuple tuples
   
   • Set multiple different values to a single data

var registrationResult = （true,"慕课女神"，"女"）let (isRegisterSuccess,nickname,gender) = registrationResultisRegisterSucss   //此处就为truenickname          //"慕课女神"gender            //"女"可以这样取值registrationResult.0   //此处就为trueregistrationResult.1   //"慕课女神"registrationResult.2   //"女"

• Omit part of a value by an underscore

let (isRegisterSuccess,_,_) = registrationResult

1. Optionals selectable values

   • Or is a value, or there is no value
   • Nil when there's no value.

a:Int?a                //此时是nila12           //此时是（Some 12）a!               //此时是12 通过！解包

• Optional binding is unpacked directly

var18iflet yourAge = age{    pringln("\(yourAge)")  }

1. Base operator

   • Assignment operation

var1var a = b

• Subtraction, Yu (die)

a530a + ba - ba * ba / b        //此处除数不能为0，求余也不能为0a % bInt.max      //整型的最大值Int.min      //整型的最小值

• "+ +", "--" self-added self-reduction

varc=0c++c--c+=2

• Comparison operator (==,! =,>,<,===,!==)

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Play Transfer swift--Study notes (continuous update)