[Swift-Summary] basic usage, swift-summary basis

[Swift-Summary] basic usage, swift-summary basis
Declare variables and constants

// Use var to declare a variable var str = "Hello, playground" str = "Hello world"; // use let to declare a constant let str1 = "I Am a handsome guy "; str1 = "I'm not a handsome guy"; // the following error will be reported: let name = "I Am a handsome guy"; // declare a constant and the type is automatically inferred as String var age: int = 20; // declare a variable to specify the proper type

Output statement

// In swift1, println is changed to print after swift2.0 ("I have said a sentence \ (name)"); print ("My age is \ (age) ");

Integer

Swift provides signed and unsigned 8-bit, 16-bit, 32-bit, and 64-bit types

Obtain the border of an integer

Let minValue = UInt8.min; // get the minimum value of the unsigned 8-bit integer let macValue = UInt8.max; // obtain the maximum value of the unsigned 8-bit integer

Int type

The int type contains almost common integers. The maximum value of a 64-bit platform is 9223372036854775807.

The above two points also apply to the unsigned type

Floating Point Number

Let pi = 3.14; // swift infers the Double type by default.

Sum of integer and floating point

Let sum = 2 + 2.14; // This does not require forced type conversion let count = 2; lei sum = pi + Double (count); // This requires forced type conversion

Typealias type with the same name

Similar to typedef in C Language

Typealias Type = UInt16; // Type is the minimum value of the UInt16 Type var TypeMin = Type. min; // UInt16

Boolean Value

Boolean values true and false in swift
Boolean values of YES and NO in OC

var flag = true;    flag = false;

Tuples

Tuples are combinations of several arbitrary types of values.
For example

Let myTuples = (20, "Boiling boiling"); // myTuples is a binary tuples. The serial number of 20 is 0, and the "Boiling boiling" is 1let myTuples1 = (20, "Boiling", "handsome guy"); // This is a triple

Access to tuples

// Use the serial number to access print ("My age is \ (myTuples.0 )"); // my age is 20 \ n // assign this tuples to another tuples receiving let (myName, myAge) = myTuples; print ("my name is \ (myName) "); // If you only need some values in the tuples, use the following method to let (age1, _) = myTuples; print (" my age is \ (age1 )");

You can also use the following method to declare and use

Let myInfo = (name: "Boiling", age: 22); print ("my name is \ (myInfo. name), my age is \ (myInfo. age )");

Optional value: optional

Optional may be a value or not a value. If it is not a value, it is nil. In swift, nil is a definite type, not a pointer.

Var myStr: String ?; // MyStr is nilvar myStr: String; // myStr is nothing

MyStr = "1234"; var num = Int (myStr); // is inferred as 1234, Int? Type var myStr1 = "hell" var num1 = Int (myStr1); // Conversion failed

Use if let to bind optional values

// Num is an optional value if let constNum = num {print ("num has a value \ (constNum )"); // num is successfully converted to positive number} else {print ("num has no value ");}

Multiple to multiple

// If num has a value, num1 has a value if let constNum = num, constNum1 = num1 {print ("num has a value of \ (constNum )");} else {print ("num has no value ");}

Optional for implicit Parsing

Implicit Parsing is optional. It is mainly used to construct a class.

Implicit choice is actually a common choice, but it can also be used as a common type.

Normal Value

Var myStr = "1234"; var num: Int? = Int (myStr); print ("\ (num !) "); // Get 1234 print (" \ (num) "); // get optional (1234); var myStr1 =" hell "var num1: Int? = Int (myStr1); print ("\ (num1 !) "); // An error is reported because no value can parse print (" \ (num1) "); // nil

Optional values

Var myStr = "1234"; var num: Int! = Int (myStr); print ("\ (num !) "); // 1234 print (" \ (num) "); // 1234var myStr1 =" hell "var num1: Int! = Int (myStr1); print ("\ (num1)"); // nilprint ("\ (num1 !) "); // Error

Error Handling

Use try catch statement or throw exception

Assertions

Assertions ensure that the value is required. Otherwise, an error will be reported.

Usage: when your value must be correct to ensure that the program runs, you can use assertions to ensure that the value is correct.

Let age =-3; assert (age> = 0, "age does not meet the requirements ");