<1>常用創(chuàng)建方法
//實(shí)例化方法創(chuàng)建

• (instancetype)initWithString:(NSString *)aString；
• (instancetype)initWithFormat:(NSString *)format, …;
• (instancetype)initWithUTF8String:(const char *)bytes;
• (instancetype)initWithCString:(const char *)nullTerminatedCString encoding:(NSStringEncoding)encoding;現(xiàn)已失效
  //類方法創(chuàng)建

• (instancetype)stringWithString:(NSString *)aString；
• (instancetype)stringWithFormat:(NSString *)format,, …；
• (instancetype)stringWithUTF8String:(const char *)bytes；
• (instancetype)stringWithCString:(const char *)cString encoding:(NSStringEncoding)enc;
  <2>求字符串長(zhǎng)度

• (NSUInteger)length;
  <3>通過(guò)索引獲取相應(yīng)的字符
• (unichar)characterAtIndex:(NSUInteger)index;
  <4>字符串比較
  //判斷兩個(gè)字符串是否相等
• (BOOL)isEqualToString:(NSString *)aString；
  //比較兩個(gè)字符串大小
• (NSComparisonResult)compare:(NSString *)aString；
  //不區(qū)分大小寫(xiě)比較大小
• (NSComparisonResult)caseInsensitiveCompare:(NSString *)aString;
  <5>字符串查找
• (NSRange)rangeOfString:(NSString *)aString;
  <6>判斷前后綴
• (BOOL)hasPrefix:(NSString *)aString;
• (BOOL)hasSuffix:(NSString ?*)aString;
  <7>數(shù)字串轉(zhuǎn)化為數(shù)字
• (double)doubleValue;
• (float)floatValue;
• (int)intValue;
• (NSInteger)integerValue ;
• (long long)longLongValue ;
• (BOOL)boolValue ;
  <8>大小寫(xiě)轉(zhuǎn)換
• (NSString *)uppercaseString;
• (NSString *)lowercaseString;
• (NSString *)capitalizedString;
  <9>字符串提取
• (NSString *)substringFromIndex:(NSUInteger)from;
• (NSString *)substringToIndex:(NSUInteger)to;
• (NSString *)substringWithRange:(NSRange)range;
  <10>從本地讀取文件內(nèi)容
• (id)initWithContentsOfFile:(NSString *)path encoding:(NSStringEncoding)enc error:(NSError **)error;

• (id)stringWithContentsOfFile:(NSString *)path encoding:(NSStringEncoding)enc error:(NSError **)error;
  <11>字符串分割
  //按照字符串整體分割

• (NSArray *)componentsSeparatedByString:(NSString *)separator;
  //按照字符集合分割
• (NSArray *)componentsSeparatedByCharactersInSet:(NSCharacterSet *)separator

1、創(chuàng)建常量字符串。

NSString *astring = @"Welcome to 1000phone";

2、通過(guò)實(shí)例化方法 initWithString:實(shí)例化一個(gè)字符串對(duì)象

NSString *astring = [[NSString alloc] initWithString:@" I love iOS!"]; NSLog(@"astring:%@",astring);
[astring release];

3、用標(biāo)準(zhǔn)c創(chuàng)建字符串: initWithCString:encoding:方法

const char *cString = "I love iphone";
NSString * aString = [[NSString alloc]initWithCString:cString encoding:NSUTF8StringEncoding];
NSLog(@"astring:%@",aString);
[aString release];
或者:用 initWithUTF8String:實(shí)例化一個(gè)字符串對(duì)象 const char *p = " Welcome to Beijing!";
NSString *string = [[NSString alloc]initWithUTF8String:p];

4、創(chuàng)建格式化字符串:占位符(由一個(gè)%加一個(gè)字符組成)

int age = 23;
NSString *astring = [[NSString alloc] initWithFormat:@”I am %d”,age]]; NSLog(@"astring:%@",astring);
[astring release];

5、通過(guò)靜態(tài)方法創(chuàng)建字符串對(duì)象

NSString * str1 = [NSString stringWithString:@"I love programming!"];
NSString * str2 = [NSString stringWithUTF8String:" I love programming!"]; NSString * str3 = [NSString stringWithFormat:@"%@",@" I love programming!"];

6. 從文件讀取字符串:initWithContentsOfFile:

NSString *path = @" /Users/qianfeng/Desktop/StringAPI.pdf"; //文件路徑 NSString *astring = [[NSString alloc] initWithContentsOfFile:path]; NSLog(@"astring:%@",astring);
[astring release];

/----------------比較兩個(gè)字符串----------------/ //用 C 比較:strcmp 函數(shù)

char string1[] = "string!";
char string2[] = "string!"; if(strcmp(string1, string2) = = 0) {
NSLog(@"1"); }

1. isEqualToString 方法 判斷兩個(gè)字符串是否相等 相等返回 1 不等返回 0

NSString *astring01 = @"This is a String!";
NSString *astring02 = @"This is a String!";
BOOL result = [astring01 isEqualToString:astring02]; NSLog(@"result:%d",result);

2. compare 方法(compare:返回的三種值 分別是-1，0，1)

//NSOrderedSame 判斷兩者內(nèi)容是否相同
NSString *astring01 = @"This is a String!";
NSString *astring02 = @"This is a String!";
BOOL result = [astring01 compare:astring02] = = NSOrderedSame;//0 NSLog(@"result:%d",result);
//NSOrderedAscending 判斷兩對(duì)象值的大小(按字母順序進(jìn)行比較，astring01 小于 astring02 為真)
NSString *astring01 = @"This is a String!";
NSString *astring02 = @"this is a String!";
BOOL result = [astring01 compare:astring02] = = NSOrderedAscending; NSLog(@"result:%d",result); //
//NSOrderedDescending 判斷兩對(duì)象值的大小(按字母順序進(jìn)行比較，astring01 大于 astring02 為真)
NSString *astring01 = @"this is a String!";
NSString *astring02 = @"This is a String!";
BOOL result = [astring01 compare:astring02] = = NSOrderedDescending; NSLog(@"result:%d",result);

3. 不考慮大小寫(xiě)比較字符串

NSString *astring01 = @"this is a String!";
NSString *astring02 = @"This is a String!";
BOOL result = [astring01 caseInsensitiveCompare:astring02] = = NSOrderedSame;
NSLog(@"result:%d",result);
enum _NSComparisonResult {
NSOrderedAscending = -1, // astring01 小于 astring02 NSOrderedSame, astring01 等于 astring02 NSOrderedDescending astring01 大于 astring02 };

/----------------改變字符串的大小寫(xiě)----------------/

NSString *string1 = @"A String";
NSString *string2 = @"String";

1. uppercaseString 小寫(xiě)轉(zhuǎn)大寫(xiě) string1 指向的對(duì)象內(nèi)容不會(huì)發(fā)生改變 (會(huì)產(chǎn)生一個(gè)新的字符串對(duì)象，string 指向這個(gè)新的對(duì)象)

NSString *string = [string1 uppercaseString];
NSLog(@"string:%@",string);

2. lowercaseString 大寫(xiě)轉(zhuǎn)小寫(xiě) string = [string1 lowercaseString]; NSLog(@"string:%@",string);

3. capitalizedString 單詞首字母大寫(xiě) 其余小寫(xiě)，其他字符保持不變 NSLog(@"string:%@",string);//首字母大小

/----------------搜索子串----------------/

NSString *string1 = @"I love iOS very much!";
NSString *string2 = @"iOS";
NSRange range = [string1 rangeOfString:string2]; //NSRange 代表一個(gè)范圍:子 串 string2 在長(zhǎng)串 string1 中的范圍(位置和長(zhǎng)度)
NSUInteger location=range.location;
NSUInteger length= range.length;
NSString *astring = [NSString stringWithFormat:@"Location:%lu,Leight:%lu",location, length]; NSLog(@"astring:%@",astring);
[astring release];

/----------------抽取子串 ----------------/

1. -substringToIndex: 從字符串的開(kāi)頭一直截取到指定的位置，但不包括該位

置的字符
NSString *string1 = @"This is a string";
NSString *string2 = [string1 substringToIndex:3]; NSLog(@"string2:%@",string2);

2. -substringFromIndex: 從指定位置開(kāi)始(包括指定位置的字符)提取，并包 括之后的全部字符 直到最后;

NSString *string1 = @"This is a string";
NSString *string2 = [string1 substringFromIndex:3]; NSLog(@"string2:%@",string2);

3. -substringWithRange: //在指定范圍內(nèi)從字符串中截取子串

NSString *string1 = @"This is a string";
NSString *string2 = [string1 substringWithRange:NSMakeRange(0, 4)]; NSLog(@"string2:%@",string2);

/------------判斷字符串內(nèi)是否還包含別的字符串(前綴，后綴)------------/ ##01:檢查字符串是否以另一個(gè)字符串開(kāi)頭- (BOOL) hasPrefix: (NSString *)

aString; (判斷前綴)
NSString *String1 = @"NSStringInformation.txt";
[String1 hasPrefix:@"NSString"] = = 1 ? NSLog(@"YES") : NSLog(@"NO"); ##02:檢查字符串是否以另一個(gè)字符串結(jié)尾- (BOOL) hasSuffix: (NSString *) aString; (判斷后綴)
[String1 hasSuffix:@".txt"] = = 1 ? NSLog(@"YES") : NSLog(@"NO");

二.NSMutableString

<1>指定索引插入子串

• (void)insertString:(NSString *)aString atIndex:(NSUInteger)loc;
  <2>刪除指定范圍的子串
• (void)deleteCharactersInRange:(NSRange)range;
  <3>追加子串
• (void)appendString:(NSString *)aString;
  <4>追加格式化子串
• (void)appendFormat:(NSString *)format, ... ;
  <5>修改字符串 覆蓋原有內(nèi)容
• (void)setString:(NSString *)aString;

/---------------給字符串分配預(yù)設(shè)空間大小----------------/ //stringWithCapacity:

NSMutableString *string;
string = [NSMutableString stringWithCapacity:20];//預(yù)設(shè)一個(gè) 20 字節(jié)的字符串 空間
string.string = @”Welcome to qianfeng”;

/---------------增加字符串----------------/

1. appendString: appendFormat: 追加，在后面追加字符串

NSMutableString *String1 = [[NSMutableString alloc] initWithString:@"This is a NSMutableString"];
//[String1 appendString:@", I will be adding some characters"];
[String1 appendFormat:[NSString stringWithFormat:@", I will be adding some characters"]];
NSLog(@"String1:%@",String1);

2. -insertString: atIndex: 在指定位置插入字符串

NSMutableString *String1 = [[NSMutableString alloc] initWithString:@"This is a NSMutableString"];
[String1 insertString:@"Hi! " atIndex:0];
NSLog(@"String1:%@",String1);

/--------在已有字符串中按照所給出范圍和長(zhǎng)度刪除字符------/

//deleteCharactersInRange: 在指定范圍內(nèi)刪除字符串
NSMutableString *String1 = [[NSMutableString alloc] initWithString:@"This is a
NSMutableString"];
[String1 deleteCharactersInRange:NSMakeRange(0, 5)]; NSLog(@"String1:%@",String1);

/--------修改字符串------/ //-setString: 修改字符串

NSMutableString *String1 = [[NSMutableString alloc] initWithString:@"This is a NSMutableString"];
[String1 setString:@"Hello Word!"];
NSLog(@"String1:%@",String1);

/--------在指定范圍內(nèi)，替換的原有的字符------/ // replaceCharactersInRange: withString: 替換

NSMutableString *String1 = [[NSMutableString alloc] initWithString:@"This is a NSMutableString"];
[String1 replaceCharactersInRange:NSMakeRange(0, 4) withString:@"That"]; NSLog(@"String1:%@",String1);

讀寫(xiě)文件
從本地讀取文件內(nèi)容

• (id)initWithContentsOfFile:(NSString *)path encoding:(NSStringEncoding)enc error:(NSError **)error;

• (id)stringWithContentsOfFile:(NSString *)path encoding:(NSStringEncoding)enc error:(NSError **)error;

NSString * readResult = [[NSString alloc]initWithContentsOfFile:@"/Users/apple/Desktop/test.txt" encoding:NSUTF8StringEncoding error:nil];
[readResult writeToFile:@"/Users/apple/Desktop/file.txt" atomically:YES encoding:NSUTF8StringEncoding error:nil];
刪除某子串
NSMutableString * s = [[NSMutableString alloc]initWithFormat:@"%d年之后，你不讓你是我",10];
NSRange range = NSMakeRange(2, 3);
[s deleteCharactersInRange:range];

字符串和文件相關(guān)的 方法
NSString * filePath = @"/Users/apple/Desktop/qfile.rar";
//取出文件的后綴名
NSString * extension = [filePath pathExtension];
//取文件名稱
NSString * lastPart =[filePath lastPathComponent];