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初学ios时候String的各种用法

时间:2014-01-25 10:38来源:未知 作者:疯狂java 点击:

  

  1. 学习方法 3

  2. NSString

  2.1. 创建常量字符串。 4

  2.2. 创建空字符串,给予赋值。 4

  2.3. 使用变量初始化 4

  2.4. 判断是否包含某字符串 4

  2.4.1. 检查字符串是否以另一个字符串开头- (BOOL) hasPrefix: (NSString *) aString; 4

  2.4.2. 是否包含其它字符 5

  2.5. 从文件读取字符串:initWithContentsOfFile方法 5

  2.6. 写字符串到文件:writeToFile方法 5

  2.7. 比较两个字符串 5

  2.7.1. 用C比较:strcmp函数 5

  2.7.2. isEqualToString方法 6

  2.7.3. compare方法(comparer返回的三种值) 6

  2.7.4. NSOrderedSame判断两者内容是否相同 6

  2.7.5. 不考虑大小写比较字符串1 7

  2.8. 改变字符串的大小写 7

  2.9. 在串中搜索子串 7

  2.10. 替换字符串 8

  2.11. 分割字符串成数组 8

  2.12. 字符串数组拼接成字符串 8

  2.13. 抽取子串 9

  2.13.1. -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 9

  2.13.2. -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 9

  2.13.3. -substringWithRange: //按照所给出的位置,长度,任意地从字符串中截取子串 9

  2.14. 扩展路径 9

  2.15. 文件扩展名 10

  2.16. 练习题:将文本“成绩单.text”内容加载到内存中并按规定的格式输出出来 10

  3. NSMutableString 10

  3.1. 给字符串分配容量 10

  3.2. 在已有字符串后面添加字符 10

  3.3. 在已有字符串中按照所给出范围和长度删除字符 11

  3.4. 在已有字符串后面在所指定的位置中插入给出的字符串 11

  3.5. 将已有的空符串换成其它的字符串 11

  3.6. 按照所给出的范围,和字符串替换的原有的字符 12

  4. NSArray 12

  4.1. 创建数组 12

  4.2. 获取指定索引处的对象; 12

  4.3. 从一个数组拷贝数据到另一数组(可变数级) 13

  4.4. 快速便利数组 14

  4.5. Copy and sort 14

  5. NSMutableArray 15

  5.1. 给数组分配容量 15

  5.2. 在数组末尾添加对象 15

  5.3. 删除数组中指定索引处对象 16

  5.4. 数组枚举 16

  5.4.1. 从前向后 16

  5.4.2. 从后向前 16

  5.5. 快速枚举 17

  6. NSDictionary 17

  6.1. 创建字典 17

  7. NSMutableDictionary 18

  7.1. 创建 18

  7.2. 添加字典 18

  7.3. 删除指定的字典 18

  8. NSValue(对任何对象进行包装) 18

  8.1. 将NSRect放入NSArray中 18

  8.2. 从Array中提取 19

  8.3. 从目录搜索扩展名为jpg的文件 19

  9. NSNumber 20
 

  NSString

  创建字符串。

  NSString *astring = @"This is a String!";

  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];

  使用变量初始化

  NSString *name = @"Ivan!";

  NSString *astring = [[NSString stringWithFormat:@”My name is %@!”,name]];

  NSLog(@"astring:%@",astring);
 

  判断是否包含某字符串

  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");
 

  是否包含其它字符

  NSString *astring = [[NSString alloc] initWithString:@"This is a String!"];

  Boolean contains = [astring rangeOfString:@”This”].length>0;

  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

  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);
 

  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);
 

  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];
 

  替换字符串

  NSString *astring01 = @"hello 中国";

  NSString * new = [astring01 stringByReplacingOccurrencesOfString:@”中国” withString:@"北京"];

  NSLog(new);
 

  分割字符串成数组

  NSString *s = @"a b d e f";

  NSArray *arr = [s componentsSeparatedByString:@" "];

  NSLog(@"count = %d",[arr count]);
 

  字符串数组拼接成字符串

  NSArray *pathArray = [NSArray arrayWithObjects:@"here",

  @"be", @"dragons", nil];

  NSLog(@"%@",[pathArray componentsJoinedByString:@""]);

  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);

  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);

  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]);
 

  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

  //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];
 

  快速便利数组

  //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];

  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];

  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

  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);

  }

  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];

  练习题:将文本“成绩单.text”内容加载到内存中并按规定的格式输出出来

  NSMutableDictionary

  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

  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);

  定义结构体并添加到NSArray里面

  typedef struct {

  float real;

  float imaginary;

  } ImaginaryNumber;

  ImaginaryNumber miNumber;

  miNumber.real = 1.1;

  miNumber.imaginary = 1.41;

  NSValue *miValue = [NSValue value:miNumber

  withObjCType:@encode(ImaginaryNumber)]; // encode using the type name

  ImaginaryNumber miNumber2;

  [miValue getValue:&miNumber2];
 

  宏定义#define讲解

  NSNumber

  NSNumber

  + (NSNumber *)numberWithInt:(int)value;

  + (NSNumber *)numberWithDouble:(double)value;

  - (int)intValue;

  - (double)doubleValue;

  NSNumber可以将基本数据类型包装起来,形成一个对象,这样就可以给其发送消息,装入NSArray中等等。

  NSNumber * intNumber=[NSNumber numberWithInt:100];

  NSNumber *floatNumber=[NSNUmber numberWithFloat:100.00];

  int i=[intNumber intValue];

  if([intNumber isEqualToNumber:floatNumber]) ....

  NSNumber继承NSObject ,可以使用比较 compare: isEqual等消息

  NSNull
 

  IOS里面最小简单的类,里面只有一个方法+(NSNull*) null;

  数学常用方法

  数学常量:

  #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)

  常用函数:

  指数运算

  NSLog(@"%.f", pow(3,2) ); //result 9

  NSLog(@"%.f", pow(3,3) ); //result 27

  开平方运算

  (计算两点间的距离时用到)

  NSLog(@"%.f", sqrt(16) ); //result 4

  NSLog(@"%.f", sqrt(81) ); //result 9

  上舍入

  NSLog(@"res: %.f", ceil(3.000000000001)); //result 4

  NSLog(@"res: %.f", ceil(3.00)); //result 3

  下舍入

  NSLog(@"res: %.f", floor(3.000000000001)); //result 3

  NSLog(@"res: %.f", floor(3.9999999)); //result 3

  四舍五入

  NSLog(@"res: %.f", round(3.5)); //result 4

  NSLog(@"res: %.f", round(3.46)); //result 3

  NSLog(@"res: %.f", round(-3.5)); //NB: this one returns -4

  最小值

  NSLog(@"res: %.f", fmin(5,10)); //result 5

  最大值

  NSLog(@"res: %.f", fmax(5,10)); //result 10

  绝对值

  NSLog(@"res: %.f", fabs(10)); //result 10

  NSLog(@"res: %.f", fabs(-10)); //result 10

  NSDate

  得到当前的日期

  NSDate *date = [NSDate date];

  日期之间比较可用以下方法

  - (BOOL)isEqualToDate:(NSDate *)otherDate;// 与otherDate比较,相同返回YES

  - (NSDate *)earlierDate:(NSDate *)anotherDate;// 与anotherDate比较,返回较早的那个日期

  - (NSDate *)laterDate:(NSDate *)anotherDate;//与anotherDate比较,返回较晚的那个日期
 

  将日期转换成字符串

  NSLog(@”date = %@”,[data description]);

  设置日期显示格式

  NSDateFormatter *formatter =[[[NSDateFormatter alloc] init] autorelease];

  [formatter setTimeStyle:NSDateFormatterFullStyle]; //设置几种默认的显示效果

  [formatter setDateFormat:@"yyyy-MM-dd HH:mm:ss a"];//设置自定义的显示效果

  NSLog([formatter stringFromDate:date]);

  NSData

  NSData-> NSString

  NSString *aString = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];

  NSString->NSData

  NSString *aString = @"1234abcd";

  NSData *aData = [aString dataUsingEncoding: NSUTF8StringEncoding];