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1. NSData 与 NSString NSData－> NSString NSString *aString = [[NSString alloc] initWithData:adataencoding:NSUTF8StringEncoding]; NSString－>NSData NSString *aString = @"1234abcd"; NSData *aData = [aString dataUsingEncoding: NSUTF8StringEncoding]; 2.NSData 与 Byte NSData－> Byte数组 NSString *testString = @"1234567890"; NSData *testData = [testString dataUsingEncoding: NSUTF8StringEncoding]; Byte *testByte = (Byte *)[testData bytes]; for(int i=0;i<[testData length];i++) printf("testByte = %d\n",testByte[i]); Byte数组－> NSData Byte byte[] = {0,1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23}; NSData *adata = [[NSData alloc] initWithBytes:byte length:24]; Byte数组－>16进制数 Byte *bytes = (Byte *)[aData bytes]; NSString *hexStr=@""; for(int i=0;i<[encryData length];i++) { NSString *newHexStr = [NSString stringWithFormat:@"%x",bytes[i]&0xff];///16进制数 if([newHexStr length]==1) hexStr = [NSString stringWithFormat:@"%@0%@",hexStr,newHexStr]; else hexStr = [NSString stringWithFormat:@"%@%@",hexStr,newHexStr]; } NSLog(@"bytes 的16进制数为:%@",hexStr); 16进制数－>Byte数组 / 将16进制数据转化成Byte 数组 NSString *hexString = @"3e435fab9c34891f"; //16进制字符串 int j=0; Byte bytes[128];  ///3ds key的Byte 数组， 128位 for(int i=0;i<[hexString length];i++) { int int_ch;  /// 两位16进制数转化后的10进制数 unichar hex_char1 = [hexString characterAtIndex:i]; 两位16进制数中的第一位(高位*16) int int_ch1; if(hex_char1 >= '0' && hex_char1 <='9') int_ch1 = (hex_char1-48)*16;    0 的Ascll - 48 else if(hex_char1 >= 'A' && hex_char1 <='F') int_ch1 = (hex_char1-55)*16; A 的Ascll - 65 else int_ch1 = (hex_char1-87)*16; a 的Ascll - 97 i++; unichar hex_char2 = [hexString characterAtIndex:i]; ///两位16进制数中的第二位(低位) int int_ch2; if(hex_char2 >= '0' && hex_char2 <='9') int_ch2 = (hex_char2-48); 0 的Ascll - 48 else if(hex_char1 >= 'A' && hex_char1 <='F') int_ch2 = hex_char2-55; A 的Ascll - 65 else int_ch2 = hex_char2-87; a 的Ascll - 97 int_ch = int_ch1+int_ch2; NSLog(@"int_ch=%d",int_ch); bytes[j] = int_ch;  ///将转化后的数放入Byte数组里 j++; } NSData *newData = [[NSData alloc] initWithBytes:bytes length:128]; NSLog(@"newData=%@",newData); 3. NSData 与 UIImage NSData－>UIImage UIImage *aimage = [UIImage imageWithData: imageData]; //例：从本地文件沙盒中取图片并转换为NSData NSString *path = [[NSBundle mainBundle] bundlePath]; NSString *name = [NSString stringWithFormat:@"ceshi.png"]; NSString *finalPath = [path stringByAppendingPathComponent:name]; NSData *imageData = [NSData dataWithContentsOfFile: finalPath]; UIImage *aimage = [UIImage imageWithData: imageData]; UIImage－> NSData NSData *imageData = UIImagePNGRepresentation(aimae); /*******************************************************************************************      NSString      *******************************************************************************************/     //一、NSString        /*----------------创建字符串的方法----------------*/     //1、创建常量字符串。     NSString *astring = @"This is a String!";     //2、创建空字符串，给予赋值。     NSString *astring = [[NSString alloc] init];     astring = @"This is a String!";     NSLog(@"astring:%@",astring);   [astring release];     //3、在以上方法中，提升速度:initWithString方法     NSString *astring = [[NSString alloc] initWithString:@"This is a String!"];     NSLog(@"astring:%@",astring);     [astring release];     //4、用标准c创建字符串:initWithCString方法     char *Cstring = "This is a String!";     NSString *astring = [[NSString alloc] initWithCString:Cstring];     NSLog(@"astring:%@",astring);     [astring release];     //5、创建格式化字符串:占位符（由一个%加一个字符组成）     int i = 1;     int j = 2;     NSString *astring = [[NSString alloc] initWithString:[NSString stringWithFormat:@"%d.This is %i string!",i,j]];     NSLog(@"astring:%@",astring);     [astring release];     //6、创建临时字符串     NSString *astring;     astring = [NSString stringWithCString:"This is a temporary string"];     NSLog(@"astring:%@",astring);     /*----------------从文件读取字符串:initWithContentsOfFile方法----------------*/        NSString *path = @"astring.text";     NSString *astring = [[NSString alloc] initWithContentsOfFile:path];     NSLog(@"astring:%@",astring);     [astring release];     /*----------------写字符串到文件:writeToFile方法----------------*/        NSString *astring = [[NSString alloc] initWithString:@"This is a String!"];     NSLog(@"astring:%@",astring);     NSString *path = @"astring.text";        [astring writeToFile: path atomically: YES];     [astring release];        /*----------------比较两个字符串----------------*/            //用C比较:strcmp函数     char string1[] = "string!";     char string2[] = "string!";     if(strcmp(string1, string2) = = 0)     {         NSLog(@"1");     }     //isEqualToString方法        NSString *astring01 = @"This is a String!";     NSString *astring02 = @"This is a String!";     BOOL result = [astring01 isEqualToString:astring02];     NSLog(@"result:%d",result);     //compare方法(comparer返回的三种值)        NSString *astring01 = @"This is a String!";     NSString *astring02 = @"This is a String!";        BOOL result = [astring01 compare:astring02] = = NSOrderedSame;        NSLog(@"result:%d",result);        //NSOrderedSame判断两者内容是否相同     NSString *astring01 = @"This is a String!";     NSString *astring02 = @"this is a String!";     BOOL result = [astring01 compare:astring02] = = NSOrderedAscending;        NSLog(@"result:%d",result);     //NSOrderedAscending判断两对象值的大小(按字母顺序进行比较，astring02大于astring01为真)     NSString *astring01 = @"this is a String!";     NSString *astring02 = @"This is a String!";     BOOL result = [astring01 compare:astring02] = = NSOrderedDescending;        NSLog(@"result:%d",result);         //NSOrderedDescending判断两对象值的大小(按字母顺序进行比较，astring02小于astring01为真)     //不考虑大小写比较字符串1     NSString *astring01 = @"this is a String!";     NSString *astring02 = @"This is a String!";     BOOL result = [astring01 caseInsensitiveCompare:astring02] = = NSOrderedSame;        NSLog(@"result:%d",result);         //NSOrderedDescending判断两对象值的大小(按字母顺序进行比较，astring02小于astring01为真)     //不考虑大小写比较字符串2     NSString *astring01 = @"this is a String!";     NSString *astring02 = @"This is a String!";     BOOL result = [astring01 compare:astring02                             options:NSCaseInsensitiveSearch | NSNumericSearch] = = NSOrderedSame;        NSLog(@"result:%d",result);         //NSCaseInsensitiveSearch:不区分大小写比较 NSLiteralSearch:进行完全比较，区分大小写 NSNumericSearch:比较字符串的字符个数，而不是字符值。     /*----------------改变字符串的大小写----------------*/        NSString *string1 = @"A String";     NSString *string2 = @"String";     NSLog(@"string1:%@",[string1 uppercaseString]);//大写     NSLog(@"string2:%@",[string2 lowercaseString]);//小写     NSLog(@"string2:%@",[string2 capitalizedString]);//首字母大小     /*----------------在串中搜索子串----------------*/            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]];     NSLog(@"astring:%@",astring);     [astring release];     /*----------------抽取子串 ----------------*/            //-substringToIndex: 从字符串的开头一直截取到指定的位置，但不包括该位置的字符     NSString *string1 = @"This is a string";     NSString *string2 = [string1 substringToIndex:3];     NSLog(@"string2:%@",string2);     //-substringFromIndex: 以指定位置开始（包括指定位置的字符），并包括之后的全部字符     NSString *string1 = @"This is a string";     NSString *string2 = [string1 substringFromIndex:3];     NSLog(@"string2:%@",string2);     //-substringWithRange: //按照所给出的位置，长度，任意地从字符串中截取子串     NSString *string1 = @"This is a string";     NSString *string2 = [string1 substringWithRange:NSMakeRange(0, 4)];     NSLog(@"string2:%@",string2);     //扩展路径     NSString *Path = @"~/NSData.txt";     NSString *absolutePath = [Path stringByExpandingTildeInPath];     NSLog(@"absolutePath:%@",absolutePath);     NSLog(@"Path:%@",[absolutePath stringByAbbreviatingWithTildeInPath]);     //文件扩展名     NSString *Path = @"~/NSData.txt";     NSLog(@"Extension:%@",[Path pathExtension]);     /*******************************************************************************************      NSMutableString      *******************************************************************************************/        /*---------------给字符串分配容量----------------*/     //stringWithCapacity:     NSMutableString *String;     String = [NSMutableString stringWithCapacity:40];     /*---------------在已有字符串后面添加字符----------------*/        //appendString: and appendFormat:     NSMutableString *String1 = [[NSMutableString alloc] initWithString:@"This is a NSMutableString"];     //[String1 appendString:@", I will be adding some character"];     [String1 appendFormat:[NSString stringWithFormat:@", I will be adding some character"]];     NSLog(@"String1:%@",String1);     */     /*--------在已有字符串中按照所给出范围和长度删除字符------*/        /*      //deleteCharactersInRange:      NSMutableString *String1 = [[NSMutableString alloc] initWithString:@"This is a NSMutableString"];      [String1 deleteCharactersInRange:NSMakeRange(0, 5)];      NSLog(@"String1:%@",String1);      /*--------在已有字符串后面在所指定的位置中插入给出的字符串------*/     //-insertString: atIndex:     NSMutableString *String1 = [[NSMutableString alloc] initWithString:@"This is a NSMutableString"];     [String1 insertString:@"Hi! " atIndex:0];     NSLog(@"String1:%@",String1);     /*--------将已有的空符串换成其它的字符串------*/     //-setString:     NSMutableString *String1 = [[NSMutableString alloc] initWithString:@"This is a NSMutableString"];     [String1 setString:@"Hello Word!"];     NSLog(@"String1:%@",String1);     /*--------按照所给出的范围，和字符串替换的原有的字符------*/     //-setString:     NSMutableString *String1 = [[NSMutableString alloc] initWithString:@"This is a NSMutableString"];     [String1 replaceCharactersInRange:NSMakeRange(0, 4) withString:@"That"];     NSLog(@"String1:%@",String1);     /*-------------判断字符串内是否还包含别的字符串(前缀，后缀)-------------*/     //01：检查字符串是否以另一个字符串开头- (BOOL) hasPrefix: (NSString *) aString;     NSString *String1 = @"NSStringInformation.txt";     [String1 hasPrefix:@"NSString"] = = 1 ?  NSLog(@"YES") : NSLog(@"NO");     [String1 hasSuffix:@".txt"] = = 1 ?  NSLog(@"YES") : NSLog(@"NO");     //02：查找字符串某处是否包含其它字符串 - (NSRange) rangeOfString: (NSString *) aString，这一点前面在串中搜索子串用到过;     /*******************************************************************************************      NSArray      *******************************************************************************************/     /*---------------------------创建数组------------------------------*/     //NSArray *array = [[NSArray alloc] initWithObjects:     @"One",@"Two",@"Three",@"Four",nil];     self.dataArray = array;     [array release];     //- (unsigned) Count;数组所包含对象个数；     NSLog(@"self.dataArray cound:%d",[self.dataArray count]);     //- (id) objectAtIndex: (unsigned int) index;获取指定索引处的对象;     NSLog(@"self.dataArray cound 2:%@",[self.dataArray objectAtIndex:2]);     /*--------------------------从一个数组拷贝数据到另一数组(可变数级)----------------------------*/        //arrayWithArray:     //NSArray *array1 = [[NSArray alloc] init];     NSMutableArray *MutableArray = [[NSMutableArray alloc] init];     NSArray *array = [NSArray arrayWithObjects:                       @"a",@"b",@"c",nil];     NSLog(@"array:%@",array);     MutableArray = [NSMutableArray arrayWithArray:array];     NSLog(@"MutableArray:%@",MutableArray);     array1 = [NSArray arrayWithArray:array];     NSLog(@"array1:%@",array1);     //Copy     //id obj;     NSMutableArray *newArray = [[NSMutableArray alloc] init];     NSArray *oldArray = [NSArray arrayWithObjects:                          @"a",@"b",@"c",@"d",@"e",@"f",@"g",@"h",nil];     NSLog(@"oldArray:%@",oldArray);     for(int i = 0; i < [oldArray count]; i++)     {                obj = [[oldArray objectAtIndex:i] copy];         [newArray addObject: obj];     }     //         NSLog(@"newArray:%@", newArray);     [newArray release];     //快速枚举     //NSMutableArray *newArray = [[NSMutableArray alloc] init];     NSArray *oldArray = [NSArray arrayWithObjects:                          @"a",@"b",@"c",@"d",@"e",@"f",@"g",@"h",nil];        NSLog(@"oldArray:%@",oldArray);     for(id obj in oldArray)     {         [newArray addObject: obj];     }     //         NSLog(@"newArray:%@", newArray);     [newArray release];        //Deep copy     //NSMutableArray *newArray = [[NSMutableArray alloc] init];     NSArray *oldArray = [NSArray arrayWithObjects:                          @"a",@"b",@"c",@"d",@"e",@"f",@"g",@"h",nil];        NSLog(@"oldArray:%@",oldArray);        newArray = (NSMutableArray*)CFPropertyListCreateDeepCopy(kCFAllocatorDefault, (CFPropertyListRef)oldArray, kCFPropertyListMutableContainers);     NSLog(@"newArray:%@", newArray);     [newArray release];        //Copy and sort     //NSMutableArray *newArray = [[NSMutableArray alloc] init];     NSArray *oldArray = [NSArray arrayWithObjects:                          @"b",@"a",@"e",@"d",@"c",@"f",@"h",@"g",nil];        NSLog(@"oldArray:%@",oldArray);     NSEnumerator *enumerator;     enumerator = [oldArray objectEnumerator];     id obj;     while(obj = [enumerator nextObject])     {         [newArray addObject: obj];     }     [newArray sortUsingSelector:@selector(compare:)];     NSLog(@"newArray:%@", newArray);     [newArray release];     /*---------------------------切分数组------------------------------*/

   1.

   //从字符串分割到数组－ componentsSeparatedByString:

    NSString *string = [[NSString alloc] initWithString:@"One,Two,Three,Four"];     NSLog(@"string:%@",string);        NSArray *array = [string componentsSeparatedByString:@","];     NSLog(@"array:%@",array);     [string release];     //从数组合并元素到字符串- componentsJoinedByString:     NSArray *array = [[NSArray alloc] initWithObjects:@"One",@"Two",@"Three",@"Four",nil];     NSString *string = [array componentsJoinedByString:@","];     NSLog(@"string:%@",string);

    2.

    NSString *a ="/pubic/evdaily.nsf/vwtrymaindocid/8E88469482579180035442A/$file/测试帐号及信息22.docx";

    NSRange range = [arangeOfString:@"$file/"];//获取$file/的位置

    NSString *b = [a substringFromIndex:range.location +  range.length];//开始截取

    NSLog(@"\n b: %@",b);

    /*******************************************************************************************      NSMutableArray      *******************************************************************************************/     /*---------------给数组分配容量----------------*/     //NSArray *array;     array = [NSMutableArray arrayWithCapacity:20];     /*--------------在数组末尾添加对象----------------*/     //- (void) addObject: (id) anObject;     //NSMutableArray *array = [NSMutableArray arrayWithObjects:     @"One",@"Two",@"Three",nil];     [array addObject:@"Four"];     NSLog(@"array:%@",array);     /*--------------删除数组中指定索引处对象----------------*/        //-(void) removeObjectAtIndex: (unsigned) index;        //NSMutableArray *array = [NSMutableArray arrayWithObjects:     @"One",@"Two",@"Three",nil];     [array removeObjectAtIndex:1];     NSLog(@"array:%@",array);     /*-------------数组枚举---------------*/        //- (NSEnumerator *)objectEnumerator;从前向后     //NSMutableArray *array = [NSMutableArray arrayWithObjects:     @"One",@"Two",@"Three",nil];     NSEnumerator *enumerator;     enumerator = [array objectEnumerator];     id thingie;     while (thingie = [enumerator nextObject]) {         NSLog(@"thingie:%@",thingie);     }     //- (NSEnumerator *)reverseObjectEnumerator;从后向前     //NSMutableArray *array = [NSMutableArray arrayWithObjects:     @"One",@"Two",@"Three",nil];     NSEnumerator *enumerator;     enumerator = [array reverseObjectEnumerator];     id object;     while (object = [enumerator nextObject]) {         NSLog(@"object:%@",object);     }     //快速枚举     //NSMutableArray *array = [NSMutableArray arrayWithObjects:     @"One",@"Two",@"Three",nil];     for(NSString *string in array)     {         NSLog(@"string:%@",string);     }     /*******************************************************************************************      NSDictionary      *******************************************************************************************/     /*------------------------------------创建字典------------------------------------*/     //- (id) initWithObjectsAndKeys;     //NSDictionary *dictionary = [[NSDictionary alloc] initWithObjectsAndKeys:@"One",@"1",@"Two",@"2",@"Three",@"3",nil];     NSString *string = [dictionary objectForKey:@"One"];     NSLog(@"string:%@",string);     NSLog(@"dictionary:%@",dictionary);     [dictionary release];     /*******************************************************************************************      NSMutableDictionary      *******************************************************************************************/     /*------------------------------------创建可变字典------------------------------------*/        //创建     NSMutableDictionary *dictionary = [NSMutableDictionary dictionary];     //添加字典     [dictionary setObject:@"One" forKey:@"1"];     [dictionary setObject:@"Two" forKey:@"2"];     [dictionary setObject:@"Three" forKey:@"3"];     [dictionary setObject:@"Four" forKey:@"4"];     NSLog(@"dictionary:%@",dictionary);     //删除指定的字典     [dictionary removeObjectForKey:@"3"];     NSLog(@"dictionary:%@",dictionary);     /*******************************************************************************************      NSValue（对任何对象进行包装）      *******************************************************************************************/     /*--------------------------------将NSRect放入NSArray中------------------------------------*/        //将NSRect放入NSArray中     NSMutableArray *array = [[NSMutableArray alloc] init];     NSValue *value;     CGRect rect = CGRectMake(0, 0, 320, 480);        value = [NSValue valueWithBytes:&rect objCType:@encode(CGRect)];     [array addObject:value];     NSLog(@"array:%@",array);     //从Array中提取     value = [array objectAtIndex:0];     [value getValue:&rect];     NSLog(@"value:%@",value);     /*******************************************************************************************      从目录搜索扩展名为jpg的文件      *******************************************************************************************/     //NSFileManager *fileManager = [NSFileManager defaultManager];     NSString *home;     home = @"../Users/";     NSDirectoryEnumerator *direnum;     direnum = [fileManager enumeratorAtPath: home];     NSMutableArray *files = [[NSMutableArray alloc] init];     //枚举     NSString *filename;     while (filename = [direnum nextObject]) {         if([[filename pathExtension] hasSuffix:@"jpg"]){             [files addObject:filename];         }     }     //快速枚举     //for(NSString *filename in direnum)     //{     //    if([[filename pathExtension] isEqualToString:@"jpg"]){     //        [files addObject:filename];     //    }     //}     NSLog(@"files:%@",files);     //枚举     NSEnumerator *filenum;     filenum = [files objectEnumerator];     while (filename = [filenum nextObject]) {         NSLog(@"filename:%@",filename);     }

参考：

http://qun.qq.com/air/#186700354/share

http://www.cnblogs.com/85538649/archive/2011/11/21/2256868.html

http://www.wezu.net/blog/archives/86