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ios app 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 = @"";
[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 = @"";
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!"];
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NSLog(@"astring:%@",astring);
NSString *path = @"";
[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
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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 = ;
int leight = ;
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
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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:
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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];
= array;
[array release];
//- (unsigned) Count;数组所包含对象个数；
NSLog(@" cound:%d",[ count]);
//获取指定索引处的对象
NSLog(@" cound 2:%@",[ 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];
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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];
}
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//
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
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//-(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);
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}
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];
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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;
= ;
= ;
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:];
int i=[intNumber intValue]；
if([intNumber isEqualToNumber:floatNumber]) ....
NSNumber 继承 NSObject ，可以使用比较 compare： isEqual 等消息
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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 // e
#define M_LOG2E // log 2e
#define M_LOG10E // log 10e
#define M_LN2 // log e2
#define M_LN10 // log e10
#define M_PI // pi
#define M_PI_2 // pi/2
#define M_PI_4 // pi/4
#define M_1_PI // 1/pi
#define M_2_PI // 2/pi
#define M_2_SQRTPI // 2/sqrt(pi)
#define M_SQRT2 // sqrt(2)
#define M_SQRT1_2 // 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()); //result 4
NSLog(@"res: %.f", ceil()); //result 3
下舍入
NSLog(@"res: %.f", floor()); //result 3
NSLog(@"res: %.f", floor()); //result 3
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四舍五入
NSLog(@"res: %.f", round()); //result 4
NSLog(@"res: %.f", round()); //result 3
NSLog(@"res: %.f", round()); //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
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encoding:NSUTF8StringEncoding];
NSString－>NSData
NSString *aString = @"1234abcd";
NSData *aData = [aString dataUsingEncoding: NSUTF8StringEncoding];
