A brief talk on the similarities and differences between OC and Swift

Swift, Apple's new development language, released in 2014 at the WWDC (Apple Developer Conference), works with objective-c* on Mac OS and iOS platforms to build apps based on Apple platforms.

It has been updated to Swift2.0 and is about to release 3.0. I heard there was a lot of change. Now let's look at the small similarities and differences between Swift and OC basics (but if it's different from OC, it feels very different.)

1. Different output logs

2. Constant variable definitions, Swift type is more accurate than OC, Swift is a type-safe language, Swift does not allow implicit conversions, but can display conversions

3. Operator: +,-, *,/,%, + +,--, OC and Swiftch In addition to the modulo operator, the OC modulo must be an integer, Swift modulo can be a decimal, Swift cannot be continuously assigned, but OC can

4. Branch

@1

1), if the parentheses after the can be omitted

2), if after can only receive bool value

3), if the curly braces cannot be omitted

@2

Swift and OC cycles are similar, but swift,for parentheses can be omitted

@3

1) While loop: the parentheses after the while can be omitted, only the bool value as the conditional statement

2) Do-while,swift in OC is used to catch anomalies, Swift uses repeat-while

There is a tuple in 4.swift, OC Wood has

5.swift Nil and OC somewhat different, OC only objects can be used Nil,swift base type (shaping, floating point) No value is also nil, when initialized, Swift can have no initial value, resulting in an optional value optional.

6.oc/swift characters are "/" ", String nsstring/string @" "/" ", OC ends with/0 string, Swift is not

1.OC output Log with NSLog

Swift prints out logs with print

Swift statement end does not need to add;

2.OC defines a constant const int a = 10;

Swift defines a constant let A = 10

OC defines the variable int a = 10;

Swift defines variable var a:int = 10

Determine the type, and then assign the value

var a:int

A = 20

Print (a)

Let A:float = 10.3//indicates 32-bit floating point type

Let b:double = 10.2//indicates 64-bit floating point type

Swift type is more accurate than OC

Let Intvalue1:int

Let Intvalue2:int16

Let Intvalue3:int32

Let Intvalue4:int64

Let Uintvalue:uint

Swift is a type-safe language, and if a direct assignment error is direct, OC will not

Let Uintvalue:uint =-10

Swift does not allow implicit conversions, but can display conversions

var a:int = 10

var b:float = Float (a)

Range operators:

Enclosing range operators:

Includes closure interval all values a...b

Semi-enclosing range operators:

Contains header does not contain tail a. <b

Scenario: Iterating through an array

For I in Arr {

}

For I in 1...5 {

Print (i)

}

For I in 1..<5 {

Print (i)

}

Bool:

C and OC do not have a true bool value

C 0 False not 0 is true

OC BOOL type typedef signed CHAR BOOL

Swift REAL BOOL

It's ture false.

If True {

Print ("Yes")

} else {

Print ("No")

}

3.

do {

index--;

}while (Index > 0)

Do in Swift is used to catch exceptions.

Repeat {

index--

Print (index)

}while (Index > 2)

4. Tuples: Enclosing multiple values of the same or different types in a single parenthesis is a tuple. Tuples and structs are similar, in fact tuples are composite types. Parentheses can be written in any type, if you do not define the type, you can automatically determine the type according to the data

The type is omitted

Let person = ("YCG", 17,180.00)

No omitted type

Let Person1: (string,int,double) = ("YCG", 17,180.00)

Get an item in a tuple

Print (person.0)

Print (PERSON.1)

Print (person.2)

The above tuple definitions have great flaws and are particularly poor in readability.

Define tuples in other ways

Omit type

Let Person2 = (name: "YCG", age:17,height:80.00)

No omitted type

Let Person3: (name:string,age:int,height:double) = (name: "YCG", age:17,height:80.00)

Get the corresponding value

Print (Person2.name)

Print (Person3.height)

Other notation for tuples

Let (name,age,height) = (name: "YCG", age:17,height:80.00)

Print (name)

Print (age)

Print (height)

5.

Defining an optional value is easy, just add one after the type. On the line. For example: Var value:int?

The difference between a optional value and a non-optional value is that the optional value is not initialized, although it is nil, but the normal variable does not even have nil.

var value:int?

Print (value)//nil

var value:int

Print (value)//Direct error

Extract the value of an optional type (forced parsing)

The optional value cannot be used directly, because the optional value has two states, one value and no value, so we need to tell the compiler if there is a value

Forces the value of an optional type to be resolved by simply adding it after the variable! We can.

var value:float?

var value2:float = value!

Print (value2)

Note: A run-time error is reported if value has no values.

When I don't know if optional has a value, how do I do it?

If the value is not nil, then the subsequent code is executed.

var value:int? = 10

If let Tmpvalue = value {//define an intermediate constant first, value does not have a value immediately and does not crash

Print (Tmpvalue)

}

Optional:??, he can make a quick judgment on nil,?? The values that follow are those that participate in the calculation

var num:int?

Let Result:int = num?? 0

Print (Result)

6.

Common methods of strings

1. Initialize empty string

Let emptystring = ""

Let emptyString2 = String ()

2. Traversing a string

Let string2 = "You are our good friend!" "

For a in string2.characters {

Print (a)

}

3. Get the length of the string

Let count = String2.characters.count

Print (count)

4. Determine if the string is empty

Let emptyStr = "1"

If Emptystr.isempty {

Print ("Yes")

}

5, the concatenation of strings

Let str1 = "Hello"

Let str2 = "world! "

Let result = str1 + str2

var str3 = "haha"

STR3 = Str3 + str2

Print (STR3)

6. Formatting strings

Let Intvalue = 10

Let STR4 = "Love"

Let STR5 = "\ (intvalue), because \ (STR4), will not be sad"

Print (STR5)

Take a decimal and then two digits

Let pi = 3.1415

Let STR6 = String (format: "%.2f", Pi)

Print (STR6)

7. String comparison

Same as the C language strcmp

Let STR7 = "a"

Let str8 = "AB"

If STR7 > Str8 {

Print (">")

} else if str7 < str8 {

Print ("<")

}

8, whether there is a prefix

Let STR9 = "www.baidu.com"

If Str9.hasprefix ("www") {

Print ("Yes")

} else {

Print ("No")

}

If Str9.hassuffix ("cm") {

Print ("Yes")

} else {

Print ("No")

}

9. Case

Let Str10 = str9.uppercasestring

Let Str11 = str9.lowercasestring

Print (STR10)

10. String to basic data type

Let Str12 = "5.2"

Let num = Float (str12)

Print (num)

11. Intercepting strings

Let Str13 = "You are our good friend!" "

Str13.startindex starting from 0 index is not an int

Let Fromstr = Str13.startIndex.advancedBy (2)

Let Tostr = Str13.endIndex.advancedBy (-2)

Let Str14 = Str13.substringfromindex (TOSTR)

Let Range:range <String.Index> = Range (Start:fromstr, END:TOSTR)

Let Str15 = Str13.substringwithrange (range)

Print (STR15)

Let ToStr1 = (Str13 as NSString). Substringtoindex (2);

Print (TOSTR1)

Let Range1 = Nsrange (Location:2, Length:6)

Let TOSTR2 = (Str13 as NSString). Substringwithrange (Range1)

Print (TOSTR2)

A brief talk on the similarities and differences between OC and Swift