Creates an empty string, given an assignment. NSString *astring = [[NSString alloc] init];astring = @ "This is a string!";
Use variable initialization nsstring *name = @ "ivan!"; NSString *astring = [[NSString stringwithformat:@ "My name is%@!", name]];
Determines whether a string is included to check whether the string begins with another string-(BOOL) Hasprefix: (NSString *) astring; NSString *string1 = @ "NSStringInformation.txt"; [String1 hasprefix:@ "nsstring"] = = 1? NSLog (@ "YES"): NSLog (@ "NO"); [String1 hassuffix:@ ". txt"] = = 1? NSLog (@ "YES"): NSLog (@ "NO"); Whether to include other characters nsstring *astring = [[NSString alloc] initwithstring:@ "This is a string!"]; Boolean contains = [astring rangeofstring:@ "This"].length>0; Read string from File: Initwithcontentsoffile method NSString *path = @ "Astring.text"; NSString *astring = [[NSString alloc] initwithcontentsoffile:path]; Write string to file: WriteToFile method NSString *astring = [[NSString alloc] initwithstring:@ "This is a string!"]; nsstring *path = @ "Astring.text"; [astring Writetofile:path Atomically:yes]; Comparison of two string isequaltostring methods NSString *astring01 = @ "This is a string!"; NSString *astring02 = @ "This is a string!"; BOOL result = [Astring01 isequaltostring:astring02]; The compare method (the three values returned by comparer) NSString *ASTRING01 = @ "This is a string!"; NSString *astring02 = @ "Thisis a string! "; BOOL result = [Astring01 compare:astring02] = = Nsorderedsame; nsorderedsame judge whether the content is the same nsstring *astring01 = @ "This is a string!"; NSString *astring02 = @ "This is a string!"; BOOL result = [Astring01 compare:astring02] = = nsorderedascending; Do not consider case comparison string 1 nsstring *astring01 = @ "This is a string!"; NSString *astring02 = @ "This is a string!"; BOOL result = [Astring01 caseinsensitivecompare:astring02] = = Nsorderedsame; Change the case of the string nsstring *string1 = @ "A string"; NSString *string2 = @ "String"; NSLog (@ "string1:%@", [string1 uppercasestring]);//Uppercase NSLog (@ "string2:%@", [string2 lowercasestring]);//lowercase NSLog (@ " string2:%@ ", [string2 capitalizedstring]);//The first letter size in the string search substring nsstring *string1 = @" This is a string "; NSString *string2 = @ "string"; Nsrange range = [string1 rangeofstring:string2]; int location = Range.location; int leight = Range.length; NSString *astring = [[NSString alloc] initwithstring:[nsstring stringwithformat:@ "location:%i,leight:%i", LocatIon,leight]]; Replace string nsstring *astring01 = @ "Hello China"; NSString * new = [ASTRING01 stringbyreplacingoccurrencesofstring:@ "China" withstring:@ "Beijing"]; Split string array nsstring *s = @ "A b d e F"; Nsarray *arr = [s componentsseparatedbystring:@ ""]; string arrays are stitched into strings nsarray *patharray = [Nsarray arraywithobjects:@ "Here" @ "Be", @ "Dragons", nil]; NSLog (@ "%@", [Patharray componentsjoinedbystring:@ ""]); extract substring-substringtoindex: From the beginning of the string to the specified position, but excluding the character of the position NSString *string1 = @ "This is a string"; NSString *string2 = [string1 substringtoindex:3]; -substringfromindex: Starts at the specified position (including the character at the specified position) and includes all subsequent characters nsstring *string1 = @ "This is a string"; NSString *string2 = [string1 substringfromindex:3]; -substringwithrange://In accordance with the given position, length, arbitrarily intercept the substring from the string nsstring *string1 = @ "This is a string"; NSString *string2 = [string1 substringwithrange:nsmakerange (0, 4)]; nsmutablestring assigning capacity to strings string = [nsmutablestring stringwithcapacity:40]; Add characters after an existing string nsmutablestring *stRing1 = [[Nsmutablestring alloc] initwithstring:@ "This is a nsmutablestring"]; [string1 appendformat:[nsstring stringwithformat:@ ", I'll be adding some character"]]; Deletes characters in an existing string according to the given range and length nsmutablestring *string1 = [[Nsmutablestring alloc] initwithstring:@ "This is a Nsmutablestring "]; [String1 deletecharactersinrange:nsmakerange (0, 5)]; Inserts the given string in the specified position after the existing string nsmutablestring *string1 = [[Nsmutablestring alloc] initwithstring:@ "This is a Nsmutablestring "]; [String1 insertstring:@] hi! [atindex:0]; Replace existing with other strings nsmutablestring *string1 = [[Nsmutablestring alloc] initwithstring:@ "This is a nsmutablestring "]; [String1 setstring:@ "Hello word!"]; The original character nsmutablestring *string1 = [[Nsmutablestring alloc] initwithstring:@ in accordance with the given range, and the string replacement Nsmutablestring "]; [String1 replacecharactersinrange:nsmakerange (0, 4) withstring:@ "that"];
Nsarray Create array Nsarray *array = [[Nsarray alloc] Initwithobjects: @ "One", @ "one", @ "three", @ "four", nil]; The number of objects contained in the array; NSLog (@ " Self.dataarray cound:%d ", [Self.dataarray Count]); Gets the object at the specified index; NSLog (@ "Self.dataarray cound 2:%@", [Self.dataarray objectatindex:2]); Copy data from one array to another nsmutablearray *mutablearray = [[Nsmutablearray alloc] init]; Nsarray *array = [Nsarray arraywithobjects: @ "A", @ "B", @ "C", nil]; mutablearray = [Nsmutablearray Arraywitharray:array]; array1 = [Nsarray Arraywitharray:array]; nsmutablearray *newarray = [[Nsmutablearray alloc] init]; nsarray *oldarray = [Nsarray arraywithobjects: @ "A", @ "B", @ "C", @ "D", @ "E", @ "F", @ "G", @ "H", nil]; for (int i = 0; i < [Oldarray count]; i++) {obj = [[Oldarray objectatindex:i] copy]; [NewArray Addobject:obj]; } Fast and convenient array nsmutablearray *newarray = [[Nsmutablearray alloc] init]; Nsarray *oldarray = [Nsarray arraywithobjects: @ "A", @ "B", @ "C", @ "D", @ "E", @ "F", @ "G", @ "H", nil]; for (id obj in oldarray) {[NewArray Addobject:obj]; } copy and sort nsmutablearray *newarray = [[Nsmutablearray alloc] init]; Nsarray *oldarray = [Nsarray arraywithobjects: @ "B", @ "a", @ "E", @ "D", @ "C", @ "F", @ "H", @ "G", nil]; nsenumerator *enumerator= [Oldarray objectenumerator]; ID obj; while (obj = [Enumerator nextobject]) {[NewArray addobject:obj];} [NewArray sortusingselector: @selector (compare:)]; Assigning capacity to arrays nsmutablearray *array = [Nsmutablearray ARRAYWITHCAPACITY:20]; Add an object at the end of the array nsmutablearray *array = [Nsmutablearray arraywithobjects: @ "One", @ "one", @ "three", nil]; [Array addobject:@ "four"]; Delete the object at the specified index in the array nsmutablearray *array = [Nsmutablearray arraywithobjects: @ "One", @ "one", @ "three", nil]; [Array removeobjectatindex:1];
Array Enumeration
Front and back
Nsmutablearray *array = [Nsmutablearray arraywithobjects: @ "One", @ "one", @ "three", nil];
Nsenumerator *enumerator = [array objectenumerator];
ID thingie;
while (thingie = [Enumerator nextobject]) {NSLog (@ "thingie:%@", thingie);}
From the back forward
Nsmutablearray *array = [Nsmutablearray arraywithobjects: @ "One", @ "one", @ "three", nil];
Nsenumerator *enumerator = [array reverseobjectenumerator];
ID object;
while (object = [Enumerator Nextobject]) {NSLog (@ "object:%@", object);}
Nsdictionary Creating a Dictionary
Nsdictionary *dictionary = [[Nsdictionary alloc] initwithobjectsandkeys:@ "One", @ "1", @ "one", @ "2", @ "three", @ "3", nil];
NSString *string = [Dictionary objectforkey:@ "One"];
Nsmutabledictionary Create
Nsmutabledictionary *dictionary = [Nsmutabledictionary dictionary];
Add a dictionary
[Dictionary setobject:@ "One" forkey:@ "1"];
[Dictionary setobject:@ "," forkey:@ "2"];
[Dictionary setobject:@ "three" forkey:@ "3"];
[Dictionary setobject:@ "Four" forkey:@ "4"];
NSLog (@ "dictionary:%@", dictionary);
Delete the specified dictionary
[Dictionary removeobjectforkey:@ "3"];
NSLog (@ "dictionary:%@", dictionary);
Nsvalue (Wrapping any object)
Macro Definition # define Explanation
NSNumber can wrap a basic data type to form an object so that it can be sent messages, loaded into Nsarray, and so on.
NSNumber * Intnumber=[nsnumber numberwithint:100];
NSNumber *floatnumber=[nsnumber numberwithfloat:100.00];
int I=[intnumber Intvalue];
Common Methods of mathematics
Mathematical constants:
#define M_E 2.71828182845904523536028747135266250//E
#define M_LOG2E 1.44269504088896340735992468100189214//Log 2e
#define M_LOG10E 0.434294481903251827651128918916605082//log 10e
#define M_LN2 0.693147180559945309417232121458176568//log E2
#define M_LN10 2.30258509299404568401799145468436421//log E10
#define M_PI 3.14159265358979323846264338327950288//PI
#define M_PI_2 1.57079632679489661923132169163975144//PI/2
#define M_PI_4 0.785398163397448309615660845819875721//PI/4
#define M_1_PI 0.318309886183790671537767526745028724//1/PI
#define M_2_PI 0.636619772367581343075535053490057448//2/PI
#define M_2_SQRTPI 1.12837916709551257389615890312154517//2/sqrt (PI)
#define M_SQRT2 1.41421356237309504880168872420969808//sqrt (2)
#define M_SQRT1_2 0.707106781186547524400844362104849039//1/sqrt (2)
Common functions:
Exponential arithmetic
NSLog (@ "%.f", pow (3,2)); Result 9
Open square operation (used to calculate the distance between two points)
NSLog (@ "%.f", sqrt (16)); Result 4
Rounding NSLog (@ "Res:%.f", Ceil (3.000000000001)); Result 4
Under round NSLog (@ "Res:%.f", Floor (3.000000000001)); Result 3
Rounded NSLog (@ "Res:%.F", round (3.5)); Result 4
Minimum value NSLog (@ "Res:%.f", Fmin (5,10)); Result 5
Maximum value NSLog (@ "Res:%.f", Fmax (5,10)); Result 10
Absolute NSLog (@ "Res:%.f", Fabs (-10)); Result 10
NSDate gets the current date nsdate *date = [NSDate Date];
Comparisons between dates are available in the following ways
-(BOOL) Isequaltodate: (NSDate *) otherdate;//compared to otherdate, same return Yes
-(NSDate *) Earlierdate: (NSDate *) anotherdate;//compared with anotherdate, return the earlier date
-(NSDate *) Laterdate: (NSDate *) anotherdate;//compared with anotherdate, return the later date
Convert dates to Strings
NSLog (@ "date =%@", [Data description]);
Set Date display format
NSDateFormatter *formatter =[[[nsdateformatter alloc] init] autorelease];
[Formatter Settimestyle:nsdateformatterfullstyle]; Set several default display effects
[Formatter setdateformat:@ "Yyyy-mm-dd HH:mm:ss a"];//set custom display effects
NSLog ([Formatter stringfromdate:date]);
Nsdata-> NSString
NSData *data;
NSString *astring = [[NSString alloc] Initwithdata:data encoding:nsutf8stringencoding];
Nsstring->nsdata
NSString *astring = @ "1234ABCD";
NSData *adata = [astring datausingencoding:nsutf8stringencoding];
String array Dictionary date math common method
