NSString

<1>常用創建方法
//實例化方法創建

  • (instancetype)initWithString:(NSString *)aString；
  • (instancetype)initWithFormat:(NSString *)format, …;
  • (instancetype)initWithUTF8String:(const char *)bytes;
  • (instancetype)initWithCString:(const char *)nullTerminatedCString encoding:(NSStringEncoding)encoding;現已失效
    //類方法創建
  • (instancetype)stringWithString:(NSString *)aString；
  • (instancetype)stringWithFormat:(NSString *)format,, …；
  • (instancetype)stringWithUTF8String:(const char *)bytes；
  • (instancetype)stringWithCString:(const char *)cString encoding:(NSStringEncoding)enc;
    <2>求字符串長度
  • (NSUInteger)length;
    <3>通過索引獲取相應的字符
  • (unichar)characterAtIndex:(NSUInteger)index;
    <4>字符串比較
    //判斷兩個字符串是否相等
  • (BOOL)isEqualToString:(NSString *)aString；
    //比較兩個字符串大小
  • (NSComparisonResult)compare:(NSString *)aString；
    //不區分大小寫比較大小
  • (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>數字串轉化為數字
  • (double)doubleValue;
  • (float)floatValue;
  • (int)intValue;
  • (NSInteger)integerValue ;
  • (long long)longLongValue ;
  • (BOOL)boolValue ;
    <8>大小寫轉換
  • (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、創建常量字符串。

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

2、通過實例化方法 initWithString:實例化一個字符串對象

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

3、用標準c創建字符串: 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:實例化一個字符串對象 const char *p = " Welcome to Beijing!";
NSString *string = [[NSString alloc]initWithUTF8String:p];

4、創建格式化字符串:占位符(由一個%加一個字符組成)

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

5、通過靜態方法創建字符串對象

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];

/----------------比較兩個字符串----------------/ //用 C 比較:strcmp 函數

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

1. isEqualToString 方法 判斷兩個字符串是否相等 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 判斷兩對象值的大小(按字母順序進行比較，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 判斷兩對象值的大小(按字母順序進行比較，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----------------/

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

1. uppercaseString 小寫轉大寫 string1 指向的對象內容不會發生改變 (會產生一個新的字符串對象，string 指向這個新的對象)

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

2. lowercaseString 大寫轉小寫 string = [string1 lowercaseString]; NSLog(@"string:%@",string);

3. capitalizedString 單詞首字母大寫 其余小寫，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 代表一個范圍:子 串 string2 在長串 string1 中的范圍(位置和長度)
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字符串開頭- (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字符串結尾- (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 覆蓋原有內容
  • (void)setString:(NSString *)aString;

/---------------給字符串分配預設空間大小----------------/ //stringWithCapacity:

NSMutableString *string;
string = [NSMutableString stringWithCapacity:20];//預設一個 20 字節的字符串 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度刪除字符------/

//deleteCharactersInRange: 在指定范圍內刪除字符串
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，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);

讀寫文件
從本地讀取文件內容

  • (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];

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