Swift Foundation 1.1--Basic syntax-variables and constants

Some days ago. After the first swift developers Conference was opened. A lot of friends around OC can not restrain.

Think it's time to learn swift, after all, Swift is a trend.

It was also their repeated request, let me tidy up the swift learning experience. Today, starting with Swift's basic grammar,

definition

• letDefine constants, once assigned, do not agree to change
• varDefines a variable. Can still be changed after assignment

//define constants and set values directly LetX:Int=Ten//constant value once set, can not be changed, the following code will error//x =//Use ': type '. Only the type is defined. Without setting a value LetY:Int//constants have an opportunity to set values once. There is no problem with the following code. Because ' Y ' has not been set to a valuey =Ten//Once the value has been set. You cannot change it again. The following code will error, because ' Y ' has been set the value//y =Print(x + y)//variable can continue to change value after setting the valuevarZ:Intz = -z = $Print(x + y + z)

self-motivated deduction

• Swift can deduce the exact type of the variable according to the code on the right.
• Usually at development time. You do not need to specify the type of the variable
• Suppose you want to specify a variable. You can use it after the variable name : , and then follow the type of the variable

No implicit conversions

• Swift is extremely strict with data type requirements
• No matter what time. It's not going to be an implicit conversion.

Let & var options

• The constants should be chosen as much as possible , only if they have to be changed tovar

Swift Foundation 1.1--Basic syntax-variables and constants