Swift Learning (III.)

I. Type derivation & BASIC operations in Swift

Type deduction in Swift

• If an identifier is defined with a direct assignment, then the type of the preceding identifier can be deduced based on the type of the subsequent assignment, so that the preceding identifier (: type) can be omitted
• View identifier type: Option + left mouse button

　　

• Integral type
  • There are signed
    • 8-bit, 16-bit, 32-bit, 64-bit is the same as in C language.
    • Int: Peace table related, default equivalent to Nsinteger in OC
  • No sign
    • 8-bit, 16-bit, 32-bit, 64-bit is the same as in C language.
    • UINT: The peace table is related, the default equivalent to Nsuinteger in OC

Basic operations in Swift

• In swift, you must ensure that the type is the same when you perform the basic operation, or you will get an error
  • Operations can be performed between the same types
  • Because there is no implicit conversion in swift
• Conversion of data types
  • int type to double type: double (identifier)
  • Double type to int type: INT (identifier)

　　　　

Logical branches in Swift

One, if branch statements

• There is a certain difference between the IF statement in OC and the
  • Judgment sentence can not add ()
  • Judgment sentence result must be a true or false value

　　　　

• Correct wording:
  • Let y = 10
    If y > 0 {
    Print ("y > 0")
    } else {
    Print ("y <= 0")
    }

Second, switch branch statement

• Basic usage consistent with OC
• Different:
  • Switch can not follow ()
  • Break is not allowed after case (default is Break)
• Example:
  • Let sex = 0
    Switch Sex {
    Case 0:
    Print ("male")
    Case 1:
    Print ("female")
    Default:
    Print ("from Thailand")
    }

• Supplementary one: A case judge can judge multiple values, multiple values, separated
  • Let Sex1 = 0
    Switch Sex1 {
    Case 0, 1:
    Print ("normal")
    Default
    Print ("from Thailand")
    }

Normal person

• Add two: Fallthrough keyword can be implemented case penetrating
  • Let Sex2 = 0
    Switch Sex2 {
    Case 0:
    Print ("Normal 0")
    Fallthrough
    Case 1:
    Print ("Normal 1")
    Default
    Print ("other")
    }

Normal person 0 Normal person 1  

• Switch Special usage One: Supports floating-point type
  • Let PI = 3.14
    Switch PI {
    Case 3.14:
    Print ("π")
    Default
    Print ("notπ")
    }

• Switch Special usage Two: support string type
  • Let M = 5
    Let n = 10
    var result = 0
    Let opration = "+"
    Switch Opration {
    Case "+":
    result = m + N
    Case "-":
    result = M-n
    Case "*":
    result = M * N
    Case "/":
    result = m/n
    Default
    result = 0
    }
    
    Print (Result)

the  

• Switch Special usage two:switch support interval judgment
• There are two common types of zones in Swift
  • Opening interval: 0.. <10 said: 0~9, not including 10
  • Closed interval: 0 ... 10 means: 0~10
  • Let score = 80
    Switch Score {
    Case 0..<60:
    Print ("Failed")
    Case 60..<80:
    Print ("Pass")
    Case 80..<90:
    Print ("good")
    Case 90..<100:
    Print ("excellent")
    Default
    Print ("Out of the box")
    }

Good three or three-mesh operator (consistent with OC)

Iv. Use of Guard

• Guard is a new syntax for Swift2.0
• It is very similar to the IF statement and is designed to improve the readability of the program
• The guard statement must have an else statement with the following syntax:
  • When the conditional expression is true, skips the contents of the Else statement and executes the statement group contents
  • The conditional expression is false when the content in the Else statement is executed, and the jump statement is typically return, break, continue, and throw
• Format:
  • Guard conditional expression-else {
    Bar Change Statement
    Break
    }
    Statement Group
• Example:
  • var manAge = 18
    Func hit (age:int), Bool {
    Guard Age >=-else {
    Print ("Hitting is not illegal")
    return False
    }
    Print ("Hitting the crime")
    return True
    }
    Hit (ManAge)
  • Hitting a crime.

Loops in Swift

One, for loop

• General wording
  • for var i = 0; I < 3; i++ {
    Print (i)
    }

• Interval for loop
  • For I in0. <3 {
    Print ("--", i)
    }

• Special wording: If subscript i is not required in the For loop
  • For_in0 ... 3 {
    Print ("Hello Siri")
    }

Second, while & does while loops

• While the judgment of the while in swift must be correct and true, no 0 is True
  • var AA = 0
    While AA < 3 {
    aa++//This sentence will die if you don't write it.
    Print ("Hi Siri")
    }

• Do While loop: Use the Repeat keyword instead of the Do
  • var bb = 0
    Repeat {
    bb++
    Print ("BBB")
    } while BB > 3

BBB

Swift Learning (III.)