Quick Start-basic type (3)

 

 

1. tuples

Format variable or constant keyword tuples variable = (variable, variable ,...) Note: 1: The tuple variable is still a variable, but the expression is different from other variables.
2: () The brackets can contain N variables.

Example;

Import Foundation/* A is A tuples variable. () contains an integer and A string. the type of the tuples is an integer and A string. */var A = (1, "swift ") // The tuples variable A consists of an integer and A string. println ()

Running result

(1, swift)

 

Mport Foundationvar B = 12/* defines a tuples. The tuples are C, and the integer values B and string are put in. The type of the tuples contains an integer and a string. */var C = (B, "Swift") // The variable B is composed of an integer and a string. println (C)

Running result

(12, Swift)

 

Yuanzu access method

1:Access using anonymous tuples

Note:

1.1 The parameters of the anonymous tuples and the defined tuples must be consistent.

1.2 you need to specify individual values in the tuples. You can use (_) to ignore unnecessary values.

Example (1.1)

Import Foundationvar A = (1, "Swift") // The tuple variable A is composed of an integer and A string./* 1: A is A tuple variable, consisting of an integer and A string. 2: (B, c) It is an anonymous tuples variable 3: values corresponding to the tuples variable A, which are assigned to anonymous variables one by one. B = 1 C = "Swift" Note: The number of defined anonymous tuples must be the same as the number of defined tuples */var (B, C) = Aprintln ("B = \ (B), C = \ (C )")

Running result

B=1,C=Swift

Example (1.2)

Import Foundationvar A = (1, "Swift") // The tuple variable A is composed of an integer and A string./* 1: A is A tuple variable, consisting of an integer and A string. 2 :(_, c) It is an anonymous tuples variable. The x underscore (_) indicates omitting the value of variable 3: The value corresponding to the tuple variable A, which is assigned to the anonymous variable one by one. Note: The number of defined anonymous tuples must be the same as the number of defined tuples */var (_, B) = Aprintln ("B = \ (B )")

Running result:

B=Swift

 

2: Access through indexes (similar to array access)

Import Foundationvar A = (1, "Swift") // The tuple variable A consists of an integer and A string. println (A.0) // A.0 indicates that the first element in the access tuples is 1 println (A.1) // A.1 indicates that the second element in the access element is "Swift"

Running result

1Swift

 

3: Access through key

Note:

Premise:

1: the variables in the tuples must be accessed by dictionaries.

2: Access Method: tuples variable. key

Import Foundation/* use key to access tuples. Note: 1: The corresponding variable must be the dictionary key: value2: when accessing, The tuples variable. key */var A = (frist: "Hello", second: "swift") println (. frist) println (. second)

Running result

Helloswift

 

Ii. type conversion

1: Convert string to INTEGER (toInt ())

Import Foundation // convert string to Int type var strA = "123" var value = strA. the toInt () // toInt function converts a string to an integer println ("value = \ (value)") var strB = "12A" var value1 = strB. the toInt () // toInt function converts a string to an integer. The Conversion failed value is nilprintln ("value1 = \ (value1 )")

Running result

value=123value1=nil

 

 

Var B = A. toInt () This function string is converted to an integer.

Where B is Int? (Optional) can contain integer value and nil

Var A: Int = 10var A: Int? = 10 Differences: var A: Int? = 10 can contain not only integer values, but also nilvar A: Int = 10 can only contain integer values

2: integer for floating point type conversion (Int ())

Import Foundationvar A = 1.10 var B = Int (A) // forcibly convert the floating point type to the integer println ("B = \ (B )")

Running result

B=1

3: integer to floating point type (Double ())

Import Foundationvar A = 1 var B = Double (A) // convert integer to floating point type var C = Float (A) println ("B = \ (B) C = \ (C )")

Running result

B=1.0 C=1.0

 

Conditional statement usage (if)

 

Method 1

If Boolean {} Note: 1: if the Boolean value is true, the method 2: {} in the if statement cannot be omitted. Otherwise, the second method is reported incorrectly.
If optional value {} Note: 1: if the optional value is not equal to nil, execute Method 2: {} in the if statement. Otherwise, an error is returned.
Method 3
If let constant value = optional value {} Note: 1: if let constant value = optional value is to assign the optional value to the constant value, if the constant value is not nil, the method 2: {} in the if statement cannot be omitted. Otherwise, an error is returned.

Example

Method 1 (if + Boolean)

Import Foundationvar A = true // when the bool value behind the if statement is true, run the {} method after the if statement if A {println ("A = \ ()")} else {println ("")}

Running result

A=true

Method 2 (if + optional)

Import Foundation // ------------------------------- the optional value is not nil ---------------- var A: Int? = 10 // the type of A int? (Optional). if A is not nil, execute the if A {println ("A = \ (A)")} method in if )")} else {println ("A = nil")} // ----------------------------- you can select nil ----------------- var B: Int? // B is optional. The default value is nil if B is nil. if B is nil, The PUT Method of {} In if is not executed if B {println ("B = \ (B )")} else {println ("B = nil ")}

Running result

A=10B=nil

Method 3 (if let constant name = optional value)

 

 

Import Foundation // ----------------- The optional value of if let is not nilvar A: Int? = 10if let B = A {// explain the value of A to B if B is not nil execute the if {} method println ("B = \ (B )")} else {println ("B = nil")} // --------------- if let, the optional value is nilvar C: Int? // C is an optional value, if no value is assigned, nilif let D = C {// The value of C is assigned to D. if D is nil, the method println ("D = \ (D) In if {} is not executed) ")} else {println (" D = nil ")}

Running result

B=10D=nil

 

 

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