创建空字符串，给予赋值。
NSString *astring = [[NSString alloc] init];
astring = @"This is a String!";
使用变量初始化
NSString *name = @"Ivan!";
NSString *astring = [[NSString stringWithFormat:@”My name is %@!”,name]];
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];
写字符串到文件:writeToFile方法
NSString *astring = [[NSString alloc] initWithString:@"This is a String!"];
NSString *path = @"astring.text";
[astring writeToFile: path atomically: YES];
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];
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;
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;
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;
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]];
替换字符串 NSString *astring01 = @"hello 中国";
NSString * new = [astring01 stringByReplacingOccurrencesOfString:@”中国” withString:@"北京"];
分割字符串成数组 NSString *s = @"a b d e f";
NSArray *arr = [s componentsSeparatedByString:@" "];
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];
-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];
-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)];
NSMutableString 给字符串分配容量
String = [NSMutableString stringWithCapacity:40];
在已有字符串后面添加字符
NSMutableString *String1 = [[NSMutableString alloc] initWithString:@"This is a NSMutableString"];
[String1 appendFormat:[NSString stringWithFormat:@", I will be adding some character"]];
在已有字符串中按照所给出范围和长度删除字符
NSMutableString *String1 = [[NSMutableString alloc] initWithString:@"This is a NSMutableString"];
[String1 deleteCharactersInRange:NSMakeRange(0, 5)];
在已有字符串后面在所指定的位置中插入给出的字符串
NSMutableString *String1 = [[NSMutableString alloc] initWithString:@"This is a NSMutableString"];
[String1 insertString:@"Hi! " atIndex:0];
将已有的换成其它的字符串
NSMutableString *String1 = [[NSMutableString alloc] initWithString:@"This is a NSMutableString"];
[String1 setString:@"Hello Word!"];
按照所给出的范围，和字符串替换的原有的字符
NSMutableString *String1 = [[NSMutableString alloc] initWithString:@"This is a NSMutableString"];
[String1 replaceCharactersInRange:NSMakeRange(0, 4) withString:@"That"];
NSArray 创建数组
NSArray *array = [[NSArray alloc] initWithObjects: @"One",@"Two",@"Three",@"Four",nil];
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
NSMutableArray *MutableArray = [[NSMutableArray alloc] init];
NSArray *array = [NSArray arrayWithObjects: @"a",@"b",@"c",nil];
MutableArray = [NSMutableArray arrayWithArray:array];
array1 = [NSArray arrayWithArray:array];
NSMutableArray *newArray = [[NSMutableArray alloc] init];
NSArray *oldArray = [NSArray arrayWithObjects: @"a",@"b",@"c",@"d",@"e",@"f",@"g",@"h",nil];
for(int i = 0; i < [oldArray count]; i++) {
obj = [[oldArray objectAtIndex:i] copy];
[newArray addObject: obj];
}
快速便利数组
NSMutableArray *newArray = [[NSMutableArray alloc] init];
NSArray *oldArray = [NSArray arrayWithObjects: @"a",@"b",@"c",@"d",@"e",@"f",@"g",@"h",nil];
for(id obj in oldArray) {
[newArray addObject: obj];
}
Copy and sort
NSMutableArray *newArray = [[NSMutableArray alloc] init];
NSArray *oldArray = [NSArray arrayWithObjects: @"b",@"a",@"e",@"d",@"c",@"f",@"h",@"g",nil];
NSEnumerator *enumerator= [oldArray objectEnumerator];
id obj;
while(obj = [enumerator nextObject]) {
[newArray addObject: obj];
}
[newArray sortUsingSelector:@selector(compare:)];
给数组分配容量
NSMutableArray *array = [NSMutableArray arrayWithCapacity:20];
在数组末尾添加对象
NSMutableArray *array = [NSMutableArray arrayWithObjects: @"One",@"Two",@"Three",nil];
[array addObject:@"Four"];
删除数组中指定索引处对象
NSMutableArray *array = [NSMutableArray arrayWithObjects: @"One",@"Two",@"Three",nil];
[array removeObjectAtIndex:1];
数组枚举
从前向后
NSMutableArray *array = [NSMutableArray arrayWithObjects: @"One",@"Two",@"Three",nil];
NSEnumerator *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 = [array reverseObjectEnumerator];
id object;
while (object = [enumerator nextObject]) { NSLog(@"object:%@",object); }
NSDictionary 创建字典
NSDictionary *dictionary = [[NSDictionary alloc] initWithObjectsAndKeys:@"One",@"1",@"Two",@"2",@"Three",@"3",nil];
NSString *string = [dictionary objectForKey:@"One"];
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）
宏定义#define讲解
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]；
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
开平方运算 （计算两点间的距离时用到）
NSLog(@"%.f", sqrt(16) ); //result 4
上舍入 NSLog(@"res: %.f", ceil(3.000000000001)); //result 4
下舍入 NSLog(@"res: %.f", floor(3.000000000001)); //result 3
四舍五入 NSLog(@"res: %.f", round(3.5)); //result 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
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－> NSString
NSData *data；
NSString *aString = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
NSString－>NSData
NSString *aString = @"1234abcd";
NSData *aData = [aString dataUsingEncoding: NSUTF8StringEncoding];