Swift BASICS (I)

1: Hello World

import Foundationprintln("hello world")

In this way, a piece of code can print out Hello world without adding ";" if you add ";", it can also run. It seems that it is to avoid the trouble. It is no longer like the C language. ";" is added at the end of every sentence of code. Similarly, in philosophy, every sentence of code is added "; "equal to not adding"; ", but writing every time is troublesome!

2: code comments, the same as the C language "//" and "/**/"

3: println () Output

If you want to output variables

VaR ftmp = 8.9 println ("\ (ftmp)") // the formatting of println is done by "\ ()". This is a omnipotent thing, replace the C language printf () with % s, % d, % C, % F to format and write parameters. I guess the reason is that he can reason for the type of the variable, so he formatted the data type himself,

4: constants and variables

You must declare before use. The statement uses ":"

var strMsg: StringstrMsg = "I‘m swift"

VaR strmsg: string? // Nil

 

Let IMAX = 10 // constant, which must be initialized and cannot be modified again
// IMAX = 9 Compilation failed. It may be similar to const modification in C language.
VaR imini = 3 // variable, which can be not initialized

VaR itmp: int32 // variable declaration. Itmp = 44 not initialized // variable assignment

Here, swift uses the reasoning type for the data type, and its reasoning type also complies with the compatible rules for data type conversion in C language.

VaR ftmp = 8.9 ftmp = 9 println ("\ (ftmp)") // here the reasoning is that ftmp is of the float type, so here when ftmp = 9, you can convert integer 9 to float. So you can see that the output is 9.0.
But not vice versa.

VaR ftmp = 8

// Ftmp = 9.02 compilation failed.

Multiple variables can be defined at a time.

VaR itmp = 9, itex = 9.8 // here, the type inference of each variable is independent. // Itmp = 8.99 error // itmp is deduced as Int. The itex reasoning is float.

VaR red, green, blue: Double // indicates that all three variables are of the double type.

Variable names and constant names support Unicode. In this way, Chinese characters or other characters can be used, but I don't think so.

5: int Data Type

Int data indicates the range. Max can be used.

let minValue = UInt8.min  // minValue is equal to 0, and is of type UInt8let maxValue = UInt8.max  // maxValue is equal to 255, and is of type UInt8

Int indicates the int64 of int32 and 64-bit systems based on the system.

Uint indicates uint32 and uint64 in 64-bit systems based on the system.

let decimalInteger = 17let binaryInteger = 0b10001       // 17 in binary notationlet octalInteger = 0o21           // 17 in octal notationlet hexadecimalInteger = 0x11     // 17 in hexadecimal notation

Type conversion

VaR dbvar: doubledbvar = 9.9let Ivar = int (dbvar) println ("\ (Ivar)") var strint = "123" Var Ivar = strint. if toint () is successful, Ivar returns int; otherwise, Nil is returned.

6: bool this type is clear as "true" and "false"

If statement only checks bool type

Let iflag = 1if iflag {// compilation failed, 1 is not a logical value}

Let iflag = 1if 1 = iflag {// Yes}

7: Use () to enclose the tuples

let tupError = (500, "httpError")let (errorCode, errorMsg) = tupErrorprintln("\(errorCode)")//500println("\(errorMsg)")// httpError

You can also define the name tuples.

let tupError = (errorCode :500, errorMsg:"httpError")println("\(errorCode)")//500println("\(errorMsg)")// httpError

8: Nil Swift's nil is different from other languages. For example, OC indicates a null pointer, while swift indicates no value. The type is not limited to the pointer type. Nil can be set to any type in swift

var iFlag :Int?iFlag = niliFlag = 9