• 創(chuàng)建常量字符串
• 創(chuàng)建空字符串
• initWithString方法
• 用標準C創(chuàng)建字符串
• 創(chuàng)建格式化字符串
• 創(chuàng)建臨時字符串
• 從文件創(chuàng)建字符串
• 用字符串創(chuàng)建字符串何乎，并寫入到文件
• 用C比較:strcmp函數
• isEqualToString方法
• compare方法
• 不考慮大小寫比較字符串
• 輸出大寫或者小寫字符串
• rangeOfString:方法
• substringToIndex:方法
• substringFromIndex:
• substringWithRange:
• stringWithCapacity:
• appendString:和appendFormat:
• insertString:atIndex:方法
• setString: 方法
• replaceCharactersInRange: withString:
• hasPrefix: 和hasSuffix:

1拔疚、從文件創(chuàng)建字符串

創(chuàng)建常量字符串

NSString*aString = @”This is a String”;
NSLog(@”string = %@”,aString);
打恿圮健：sring ＝ThisisaString

創(chuàng)建空字符串领曼，給予賦值

NSString *aString = [[NSString  alloc]  init];
aString = @”This is a String”;
NSLog(@”string = %@”,aString);
打幽ㄊ！：sring ＝ThisisaString

initWithString方法

作用：相對上面的方法可提升速度
NSString *astring = [[NSString  alloc]  initWithString:@"This is aString!"];

用標準C創(chuàng)建字符串

方法：initWithCString
char *cString = ”This is a String”;
NSString *astring = [[NSString  alloc]  initWithCString:Cstring];
NSLog(@”string = %@”,aString);
打铀颈А：sring ＝ThisisaString

創(chuàng)建格式化字符串

占位符：由一個％加一個字符組成蓖康。
inti = 1;
intj = 2;
 NSString *aString= [[NSString  alloc]  initWithString:[NSString  stringWithFormat:@“i is %d, j is %d”,i,j]];
NSLog(@”string = %@”,aString);
打宇盱拧：string=i is 1, j is 2

創(chuàng)建臨時字符串

NSString *aString;
aString= [NSString  stringWithCString:“Thisis a temporary string”];
NSLog(@”aString = %@”,aString);
打印：aString = This is a temporary string

從文件創(chuàng)建字符串

獲取文件路徑
NSString*path = [[NSBundle mainBundle]  pathForResource:@“aString.text”ofType:nil];
NSString*aString= [[NSString  alloc]  initWithContentsOfFile:path];

2蒜焊、用字符串創(chuàng)建字符串倒信，并寫入到文件

用字符串創(chuàng)建字符串
NSString*aString = [[NSString  alloc]  initWithString:@“Thisis a String!”];
保存到的文件
NSString*path = @“astring.text”;
寫入文件
[aString writeToFile: path atomically: YES];

3、用C比較:strcmp函數

char string1[] = “string!”;
 char string2[] =“string!”;
 if(strcmp(string1, string2) == 0) {
  NSLog(@“1”);
}
說明：strcmp()用來比較字符串（區(qū)分大小寫）泳梆，其原型為：    intstrcmp(constchar *s1,constchar *s2);

4鳖悠、isEqualToString方法

比較兩個字符串是否相等唆迁，返回布爾類型BOOL
NSString *aString01= @“This is a String!”;
 NSString *aString02= @“This is a String!”;
BOOL result = [aString01  isEqualToString:aString02];

5、compare方法

comparer返回的三種值：
NSOrderedSame判斷兩者內容是否相同
NSOrderedAscending判斷兩對象值的大小(按字母升序進行比較竞穷，aString02大于aString01為真)
NSOrderedDescending判斷兩對象值的大小(按字母將序進行比較唐责，aString02小于aString01為真)

NSOrderedSame判斷兩者內容是否相同
NSString *aString01= @“This is a String!”;
NSString*aString02= @“This is a String!”;
 BOOL result = [aString01 compare:aString02] ==NSOrderedSame;
if (result){
  //為真
  NSLog(@”真”);
}

NSOrderedAscending判斷兩對象值的大小(按字母順序進行比較，aString02大于aString01為真)
NSString *aString01= @"This is aString!";
NSString*aString02= @"this is aString!";
BOOL result = [aString01  compare:aString02] ==NSOrderedAscending;
if (result){
  //為真
  NSLog(@”真”);
}

NSOrderedDescending判斷兩對象值的大小(按字母順序進行比較瘾带，aString02小于aString01為真)
NSString *aString01= @"this is a String!";
NSString *aString02= @"This is aString!";
BOOL result = [aString01 compare:aString02] ==NSOrderedDescending;
if (result){
  //為真
  NSLog(@”真”);
}

6鼠哥、不考慮大小寫比較字符串

NSString *astring01 = @"this is a String!";
NSString*astring02 = @"This is a String!";
 BOOL result = [astring01  caseInsensitiveCompare:astring02] ==NSOrderedSame;
 //NSOrderedDescending判斷兩對象值的大小(按字母順序進行比較，astring02小于astring01為真)

NSString *astring01 = @"this is a String!";
 NSString *astring02 = @"This is a String!";
 BOOL result = [astring01  compare:astring02options:NSCaseInsensitiveSearch |NSNumericSearch] ==NSOrderedSame;
//NSCaseInsensitiveSearch:不區(qū)分大小寫比較NSLiteralSearch:進行完全比較看政，區(qū)分大小寫NSNumericSearch:比較字符串的字符個數朴恳，而不是字符值。 

7允蚣、輸出大寫或者小寫字符串

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

NSLog(@"string1:%@",[string1 uppercaseString]);//大寫
打佑谟薄：string1: A STRING

NSLog(@"string2:%@",[string2 lowercaseString]);//小寫
打印：string2: string

NSLog(@“string2:%@”,[string2 capitalizedString]);//首字母大寫
打尤峦谩：String

#### 8森渐、rangeOfString:方法

查找字符串某處是否包含其它字符串。
NSString string1 =@“This is astring”;
NSStringstring2 =@“string”;
NSRange range = [string1 rangeOfString:string2];
intlocation = range.location;//字符串所在位置
NSString*aString= [[NSString alloc] initWithString:[NSString stringWithFormat:@“Location:%i,Leight:%i”,location,leight]];
NSLog(@”aString:%@",aString);
打用拔：aString:Location:10,Leight:6

#### 9同衣、substringToIndex:方法

從字符串的開頭一直截取到指定的位置，但不包括該位置的字符壶运。
NSString string1 =@“This is astring”;
NSStringstring2 = [string1 substringToIndex:3];
NSLog(@"string2:%@",string2);
打幽推搿：string2: Thi

#### 10、substringFromIndex:

以指定位置開始（包括指定位置的字符）蒋情，并包括之后的全部字符埠况。
NSString *string1 =@“This is astring”;
NSString *string2 = [string1 substringFromIndex:3];
NSLog(@“string2:%@”,string2);
打印：string2: s is a string

#### 11棵癣、substringWithRange: 

按照所給出的位置辕翰，長度，任意地從字符串中截取子串浙巫。
NSString string1 =@“This is astring”;
NSStringstring2 = [string1 substringWithRange:NSMakeRange(0, 4)];
NSLog(@“string2:%@”,string2);

#### 12金蜀、stringWithCapacity: 

按照固定長度生成空字符串刷后。
NSMutableString *String;
String = [NSMutableString stringWithCapacity:40];
這是初始化一個可變的字符串

#### 13的畴、appendString:和appendFormat: 

把一個字符串接在另一個字符串的末尾。
NSMutableString *String1 = [[NSMutableString alloc] initWithString:@"This is aNSMutableString"];
[String1 appendString:@", Yes"];
[String1 appendFormat:[NSString stringWithFormat:@",it is"]];
NSLog(@"String1:%@",String1);
打映⒌ā：String1: :This isaNSMutableString, Yes, it is

#### 14丧裁、insertString:atIndex:方法

在指定位置插入字符串。
NSMutableString *String1 = [[NSMutableString alloc] initWithString:@“This is a NSMutableString”];
[String1 insertString:@“Hi!” atIndex:0];//在第0個位置插入
NSLog(@“String1:%@”,String1);
打雍巍：String1: Hi! This is a NSMutableString

#### 15煎娇、setString: 方法

替換原來的值二庵。
NSMutableString *String1 = [[NSMutableString alloc] initWithString:@"This is a NSMutableString"];
[String1 setString:@"Hello Word!"];
NSLog(@“String1:%@”,String1);
打印：String1: Hello Word!

#### 16缓呛、replaceCharactersInRange: withString:

用指定字符串替換字符串中某指定位置催享、長度的字符串。
NSMutableString *String1 = [[NSMutableString alloc] initWithString:@“This is a NSMutableString”];
[String1 replaceCharactersInRange:NSMakeRange(0, 4)withString:@“That”]; //從第0個位置開始長度是4（This）用That來替換
NSLog(@“String1:%@”,String1);
打佑窗怼：String1: That is a NSMutableString

#### 17因妙、hasPrefix: 和hasSuffix:

>檢查字符串是否以另一個字符串開頭和是否以一個字符串結尾。
NSString *String1 =@“NSStringInformation.txt”;

[String1 hasPrefix:@“NSString”] == 1 ? NSLog(@“YES”): NSLog(@“NO”);
打悠彼琛：YES

[String1 hasSuffix:@“.txt”]= = 1 ? NSLog(@“YES”): NSLog(@“NO”);
打优屎：YES

說明：用到的“？：” 是三目運算符