iOS开发宝典:String用法大全
一、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); 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];
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]; 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]);
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