OC Strings and values

1??. NSString

In C, strings are made up of char (ASCII) characters, each of which takes one byte

In OC, the string is composed of Unichar (Unicode) characters, each of which occupies two bytes

NSString: Immutable string, that is: after creation, content and length cannot be changed

Nsmutablestring: variable string, that is: After creation, the content can also be modified

1. > Creation of strings

> Open Space, Initialize

NSString *string = [[NSString alloc] initwithformat:@ "I love IOS"];

> Convenience Builder

NSString *string = [NSString stringwithformat:@ "I love IOS"];

> Literal--laughter grammar, grammar sugar

NSString *string = @ "I love IOS";

Get string Length:

NSLog (@ "%d", string.length);

Get string in string

-(Unichar) Characteratindex: (Nsuinteger) Indes;

Determine if two strings are equal

[String isequaltostring:string1];(return value is type bool)

Comparison of strings

-(Nscomparisonresult) Compare: (NSString *) string;

Get substring

-(NSString *) Substringfromindex: (Nsuinteger) from;

-(NSString *) Substringtoindex: (Nsuinteger) to;

Stitching strings
-(NSString *) Stringbyappendingformat: (NSString *) format, ...;

Replace string

-(NSString *) Stringbyreplacingcharactersinrange: (nsrange) Range withstring: (NSString *) Replacement;

string conversion to int type

@property (readonly) int intvalue;

String all uppercase

@property (readonly, copy) NSString *uppercasestring;

String All lowercase

@property (readonly, copy) NSString *lowercasestring;

Capitalize the first letter of each string separated by a space number

@property (readonly, copy) nsstring*capitalizedstring;

Whether to prefix the specified string

-(BOOL) Hasprefix: (NSString *) str;

Like what:

NSString *string = [NSString stringwithformat:@ "Hello.png"];

BOOL isture = [string hasprefix:@ "Hello"];

if (1 = = isture) {

NSLog (@ "string is preceded by Hello");
} else {

NSLog (@ "string not preceded by Hello");

}

Whether to suffix with the specified string

-(BOOL) Hassuffix: (NSString *) str;

2??. > Variable String nsmutablestring

The string created by nsmutablestring is a dynamic variable string that can be added, deleted, changed, and manipulated for the original string object.

Immutable string--cannot be modified by itself

The modification of an immutable string is done by a copy of the original string, and a new string is obtained.

Variable string--can be modified by itself

mutable strings Modify the original string, so the action method of a mutable string does not return a value!!

Initialize method

-(Nsmutablestring *) initwithcapacity: (Nsuinteger) capacity

Convenience Builder

+ (nsmutablestring *) stringwithcapacity: (Nsuinteger) capacity;

The capacity--parameter value is the estimated space size, but dynamically adjusts the actual space size according to the actual storage situation

Mutable strings also have their own concatenation of string methods

-(void) AppendFormat: (NSString *) format, ...;

Note: nsmutablestring can complete the deletion of the string itself, but if you call the parent class NSString specific methods, there may be some errors such as

nsmutablestring *mstr = [nsmutablestring stringwithformat:@ "Hello World"];

[Mstr stringbyappendingformat:@ "Hello"];

NSLog (@ "%@", MSTR);

This output is still hello world.

Insert String

-(void) insertstring: (NSString *) astring Atindex: (nsuinteger) Loc;

Delete a string

-(void) Deletecharactersinrange: (nsrange) range;

Replace string

-(void) Replacecharactersinrange: (nsrange) Range withstring: (NSString *) astring;

Reset String
-(void) setString: (NSString *) astring;

2?? 1.> an integer 123, stored as an object of type NSNumber.

int b = 123;

NSNumber *number1 = [NSNumber numberwithint:b];

NSLog (@ "number1 =%@", number1);

int B1 = [Number1 intvalue];

NSLog (@ "result =%d", B1);

2.> 3.14159, which is stored as an object of type NSNumber.

float C = 3.14159;

NSNumber *number2 = [NSNumber numberwithfloat:c];

NSLog (@ "number2 =%@", number2);

float C1 = [number2 floatvalue];

NSLog (@ "result =%f", C1);

3.> ' C ' is stored as an object of type NSNumber.

Char d = ' C ';

NSNumber *number3 = [NSNumber numberwithchar:d];

NSLog (@ "Number3 =%@", Number3);

char D1 = [Number3 charvalue];

NSLog (@ "result =%c", D1);

4.> will save Yes as an object of type NSNumber.

BOOL e = YES;

NSNumber *number4 = [NSNumber numberwithbool:e];

NSLog (@ "number4 =%@", number4);

BOOL e1 = [Number4 boolvalue];

NSLog (@ "result =%d", E1);

3?? 1.> defines the student structure, including name, gender, age, score, and number; Defines the variable for the struct and stores it as an object of type Nsvalue.

typedef struct student{

Char name[20];//name

Char gender;//Sex

int age;//Age

int score;//fraction

int number;//No.

}student;

Student stu = {"Xiaoming", ' m ', 18, 88, 6};

Nsvalue *stu = [Nsvalue valuewithbytes:&stu objctype: @encode (Student)];

NSLog (@ "Stu =%@", Stu);

OC in the MRC environment can be such a structure

typedef struct STUDENT {

NSString *name;//Name

NSString *gender;//Sex

Nsinteger age;//Age

Nsinteger score;//Score

Nsinteger number;//School Number

}student;

Student student1 = {@ "xiaoming", @ "male", 18, 88, 6};

Class method

Nsvalue *stu =[nsvalue value:&student1 withobjctype: @encode (Student)];

//

Object methods

Nsvalue *STU1 = [[Nsvalue alloc] initwithbytes:&student1 objctype: @encode (Student)];

NSLog (@ "Stu =%@", Stu);

NSLog (@ "STU1 =%@", STU1);

2.> defines a variable of type nsrange, stored as an object of type Nsvalue.

Nsrange range = Nsmakerange (2, 5);

Nsvalue *rangev = [Nsvalue valuewithrange:range];

NSLog (@ "rangevalue =%@", Rangev);

3.> the object of the above Nsvalue type back to the corresponding data type.

Nsrange Newrange = [Rangev rangevalue];

NSLog (@ "Newrange =%@", Nsstringfromrange (Newrange));

OC Strings and values