string的使用方法

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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);
string 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);

二、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);

三、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];

快速遍历数组

     //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;
ctionary *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

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];

四、宏定义#define讲解

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