Swift basic usage-var/let defining variables and constants

Playground-noun:a place where people can playimport uikit//------------------------------------------------------- -----------------------//1. Line prints a string println ("Hello, world!") ------------------------------------------------------------------------------//2. var (variable) & Let (constant)//var variable, after assignment can be modified/allow constant, after assignment cannot modify var a = 10var b = 20let c = 30b = 30//The following code attempts to modify the constant, error//c = 40//in the spell You can use the format "\ (variable name/constant name)" When you connect a string, var result = "\ (a) + \ (b) = \ (c)"//--------------------------------------------------------- ---------------------//3. Specifying the type when defining a variable//in Swift, the type of the variable is automatically inferred at compile time//usually when the variable is defined, it is not necessary to deliberately specify the type of the variable, if you need to specify, you can follow the following format: var i:int = 20var str:string = "Hello" str + = " "str + =" Swift "result = str +" \ (i) "

Swift basic usage-var/let defining variables and constants