iOS开发宝典:String用法大全

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iOS开发宝典:String用法大全
一、NSString

创建字符串。
1. NSString *astring = @"This is a String!";
创建空字符串，给予赋值。
1. NSString *astring = [[NSString alloc] init];
3. astring = @"This is a String!";
5. NSLog(@"astring:%@",astring);
7. string release];
使用变量初始化
1. NSString *name = @"Ivan!";
2. NSString *astring = [[NSString stringWithFormat:@”My name is %@!”,name]];
3. 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
1. - (BOOL) hasPrefix: (NSString *) aString;
2. NSString *String1 = @"NSStringInformation.txt";
3. [String1 hasPrefix:@"NSString"] == 1 ? NSLog(@"YES") : NSLog(@"NO");
4. [String1 hasSuffix:@".txt"] == 1 ? NSLog(@"YES") : NSLog(@"NO");
是否包含其它字符
1. NSString *astring = [[NSString alloc] initWithString:@"This is a String!"];
2. Boolean contains = [astring rangeOfString:@”This”].length>0;
从文件读取字符串:
1. initWithContentsOfFile方法
2. NSString *path = @"astring.text";
3. NSString *astring = [[NSString alloc] initWithContentsOfFile:path];
4. NSLog(@"astring:%@",astring);
5. [astring release];
写字符串到文件:writeToFile方法
1. NSString *astring = [[NSString alloc] initWithString:@"This is a String!"];
2. NSLog(@"astring:%@",astring);
3. NSString *path = @"astring.text";
4. [astring writeToFile: path atomically: YES];
5. [astring release];
比较两个字符串

isEqualToString方法
1. NSString *astring01 = @"This is a String!";
2. NSString *astring02 = @"This is a String!";
3. BOOL result = [astring01 isEqualToString:astring02];
4. NSLog(@"result:%d",result);
compare方法(comparer返回的三种值)
1. NSString *astring01 = @"This is a String!";
2. NSString *astring02 = @"This is a String!";
3. BOOL result = [astring01 compare:astring02] = = NSOrderedSame;
4. NSLog(@"result:%d",result);
NSOrderedSame判断两者内容是否相同
1. NSString *astring01 = @"This is a String!";
2. NSString *astring02 = @"this is a String!";
3. BOOL result = [astring01 compare:astring02] = = NSOrderedAscending;
4. NSLog(@"result:%d",result);
不考虑大小写比较字符串1
1. NSString *astring01 = @"this is a String!";
2. NSString *astring02 = @"This is a String!";
3. BOOL result = [astring01 caseInsensitiveCompare:astring02] = = NSOrderedSame;
4. NSLog(@"result:%d",result);
改变字符串的大小写
1. NSString *string1 = @"A String";
2. NSString *string2 = @"String";
3. NSLog(@"string1:%@",[string1 uppercaseString]);//大写
4. NSLog(@"string2:%@",[string2 lowercaseString]);//小写
5. NSLog(@"string2:%@",[string2 capitalizedString]);//首字母大小
在串中搜索子串
1. NSString *string1 = @"This is a string";
2. NSString *string2 = @"string";
3. NSRange range = [string1 rangeOfString:string2];
4. int location = range.location;
5. int leight = range.length;
6. NSString *astring = [[NSString alloc] initWithString:[NSString stringWithFormat:@"Location:%i,Leight:%i",location,leight]];
7. NSLog(@"astring:%@",astring);
8. [astring release];
替换字符串
1. NSString *astring01 = @"hello 中国";
2. NSString * new = [astring01 stringByReplacingOccurrencesOfString:@”中国” withString:@"北京"];
3. NSLog(new);
分割字符串成数组
1. NSString *s = @"a b d e f";
2. NSArray *arr = [s componentsSeparatedByString:@" "];
3. NSLog(@"count = %d",[arr count]);
字符串数组拼接成字符串
1. NSArray *pathArray = [NSArray arrayWithObjects:@"here",
2. @"be", @"dragons", nil];
3. 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
1. NSString *string1 = @"This is a string";
2. NSString *string2 = [string1 substringToIndex:3];
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
1. NSString *string1 = @"This is a string";
2. NSString *string2 = [string1 substringFromIndex:3];
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
1. NSString *string1 = @"This is a string";
2. NSString *string2 = [string1 substringWithRange:NSMakeRange(0, 4)];
3. NSLog(@"string2:%@",string2);
二、NSMutableString

给字符串分配容量
1. //stringWithCapacity:
2. NSMutableString *String;
3. String = [NSMutableString stringWithCapacity:40];
在已有字符串后面添加字符
1. //appendString: and appendFormat:
2. NSMutableString *String1 = [[NSMutableString alloc] initWithString:@"This is a NSMutableString"];
3. //[String1 appendString:@", I will be adding some character"];
4. [String1 appendFormat:[NSString stringWithFormat:@", I will be adding some character"]];
5. NSLog(@"String1:%@",String1);
6. */
在已有字符串中按照所给出范围和长度删除字符
1. //deleteCharactersInRange:
2. NSMutableString *String1 = [[NSMutableString alloc] initWithString:@"This is a NSMutableString"];
3. [String1 deleteCharactersInRange:NSMakeRange(0, 5)];
4. 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
1. //-insertString: atIndex:
2. NSMutableString *String1 = [[NSMutableString alloc] initWithString:@"This is a NSMutableString"];
3. [String1 insertString:@"Hi! " atIndex:0];
4. NSLog(@"String1:%@",String1);
将已有的换成其它的字符串
1. //-setString:
2. NSMutableString *String1 = [[NSMutableString alloc] initWithString:@"This is a NSMutableString"];
3. [String1 setString:@"Hello Word!"];
4. NSLog(@"String1:%@",String1);
按照所给出的范围，和字符串替换的原有的字符
1. //-setString:
2. NSMutableString *String1 = [[NSMutableString alloc] initWithString:@"This is a NSMutableString"];
3. [String1 replaceCharactersInRange:NSMakeRange(0, 4) withString:@"That"];
4. NSLog(@"String1:%@",String1);
三、NSArray

创建数组
1. NSArray *array = [[NSArray alloc] initWithObjects:
2. @"One",@"Two",@"Three",@"Four",nil];
3. self.dataArray = array;
4. [array release];
5. //- (unsigned) Count;数组所包含对象个数；
6. NSLog(@"self.dataArray cound:%d",[self.dataArray count]);
7. //获取指定索引处的对象
8. NSLog(@"self.dataArray cound 2:%@",[self.dataArray objectAtIndex:2]);
从一个数组拷贝数据到另一数组
1. //arrayWithArray:
2. //NSArray *array1 = [[NSArray alloc] init];
3. NSMutableArray *MutableArray = [[NSMutableArray alloc] init];
4. NSArray *array = [NSArray arrayWithObjects:
5. @"a",@"b",@"c",nil];
6. NSLog(@"array:%@",array);
7. MutableArray = [NSMutableArray arrayWithArray:array];
8. NSLog(@"MutableArray:%@",MutableArray);
9. array1 = [NSArray arrayWithArray:array];
10. NSLog(@"array1:%@",array1);
11. //Copy
12. //id obj;
13. NSMutableArray *newArray = [[NSMutableArray alloc] init];
14. NSArray *oldArray = [NSArray arrayWithObjects:
15. @"a",@"b",@"c",@"d",@"e",@"f",@"g",@"h",nil];
16. NSLog(@"oldArray:%@",oldArray);
17. for(int i = 0; i < [oldArray count]; i++)
18. {
19. obj = [[oldArray objectAtIndex:i] copy];
20. [newArray addObject: obj];
21. }
22. //
23. NSLog(@"newArray:%@", newArray);
24. [newArray release];
快速遍历数组
1. //NSMutableArray *newArray = [[NSMutableArray alloc] init];
2. NSArray *oldArray = [NSArray arrayWithObjects:
3. @"a",@"b",@"c",@"d",@"e",@"f",@"g",@"h",nil];
4. NSLog(@"oldArray:%@",oldArray);
5. for(id obj in oldArray)
6. {
7. [newArray addObject: obj];
8. }
9. //
10. NSLog(@"newArray:%@", newArray);
11. [newArray release];
12. Copy and sort
13. //NSMutableArray *newArray = [[NSMutableArray alloc] init];
14. NSArray *oldArray = [NSArray arrayWithObjects:
15. @"b",@"a",@"e",@"d",@"c",@"f",@"h",@"g",nil];
16. NSLog(@"oldArray:%@",oldArray);
17. NSEnumerator *enumerator;
18. enumerator = [oldArray objectEnumerator];
19. id obj;
20. while(obj = [enumerator nextObject])
21. {
22. [newArray addObject: obj];
23. }
24. [newArray sortUsingSelector:@selector(compare:)];
25. NSLog(@"newArray:%@", newArray);
26. [newArray release];
27. NSMutableArray
给数组分配容量
1. //NSArray *array;
2. array = [NSMutableArray arrayWithCapacity:20];
在数组末尾添加对象
1. //- (void) addObject: (id) anObject;
2. //NSMutableArray *array = [NSMutableArray arrayWithObjects:
3. @"One",@"Two",@"Three",nil];
4. [array addObject:@"Four"];
5. NSLog(@"array:%@",array);
删除数组中指定索引处对象
1. //-(void) removeObjectAtIndex: (unsigned) index;
2. //NSMutableArray *array = [NSMutableArray arrayWithObjects:
3. @"One",@"Two",@"Three",nil];
4. [array removeObjectAtIndex:1];
5. NSLog(@"array:%@",array);
数组枚举

从前向后
1. //NSMutableArray *array = [NSMutableArray arrayWithObjects:
2. @"One",@"Two",@"Three",nil];
3. NSEnumerator *enumerator;
4. enumerator = [array objectEnumerator];
5. id thingie;
6. while (thingie = [enumerator nextObject]) {
7. NSLog(@"thingie:%@",thingie);
8. }
从后向前
1. NSMutableArray *array = [NSMutableArray arrayWithObjects:
2. @"One",@"Two",@"Three",nil];
3. NSEnumerator *enumerator;
4. enumerator = [array reverseObjectEnumerator];
5. id object;
6. while (object = [enumerator nextObject]) {
7. NSLog(@"object:%@",object);
8. }
快速枚举
1. //NSMutableArray *array = [NSMutableArray arrayWithObjects:
2. @"One",@"Two",@"Three",nil];
3. for(NSString *string in array)
4. {
5. NSLog(@"string:%@",string);
6. }
7. NSDictionary
创建字典
1. //- (id) initWithObjectsAndKeys;
2. ctionary *dictionary = [[NSDictionary alloc] initWithObjectsAndKeys:@"One",@"1",@"Two",@"2",@"Three",@"3",nil];
3. NSString *string = [dictionary objectForKey:@"One"];
4. NSLog(@"string:%@",string);
5. NSLog(@"dictionary:%@",dictionary);
6. [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
1. NSMutableDictionary *dictionary = [NSMutableDictionary dictionary];
添加字典
1. [dictionary setObject:@"One" forKey:@"1"];
2. [dictionary setObject:@"Two" forKey:@"2"];
3. [dictionary setObject:@"Three" forKey:@"3"];
4. [dictionary setObject:@"Four" forKey:@"4"];
5. NSLog(@"dictionary:%@",dictionary);
删除指定的字典
1. [dictionary removeObjectForKey:@"3"];
2. NSLog(@"dictionary:%@",dictionary);
NSValue（对任何对象进行包装）

将NSRect放入NSArray中
1. NSMutableArray *array = [[NSMutableArray alloc] init];
2. NSValue *value;
3. CGRect rect = CGRectMake(0, 0, 320, 480);
4. value = [NSValue valueWithBytes:&rect objCType:@encode(CGRect)];
5. [array addObject:value];
6. NSLog(@"array:%@",array);
从Array中提取
1. value = [array objectAtIndex:0];
2. [value getValue:&rect];
3. NSLog(@"value:%@",value);
定义结构体并添加到NSArray里面
1. typedef struct {
2. float real;
3. float imaginary;
4. } ImaginaryNumber;
5. ImaginaryNumber miNumber;
6. miNumber.real = 1.1;
7. miNumber.imaginary = 1.41;
8. NSValue *miValue = [NSValue value:miNumber
9. withObjCType:@encode(ImaginaryNumber)]; // encode using the type name
10. ImaginaryNumber miNumber2;
11. [miValue getValue:&miNumber2];
四、宏定义#define讲解

NSNumber
1. + (NSNumber *)numberWithInt:(int)value;
2. + (NSNumber *)numberWithDouble:(double)value;
3. - (int)intValue;
4. - (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。
1. NSNumber * intNumber=[NSNumber numberWithInt：100]；
2. NSNumber *floatNumber=[NSNUmber numberWithFloat:100.00];
3. int i=[intNumber intValue]；
4. 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：
1. #define M_E 2.71828182845904523536028747135266250 // e
2. #define M_LOG2E 1.44269504088896340735992468100189214 // log 2e
3. #define M_LOG10E 0.434294481903251827651128918916605082 // log 10e
4. #define M_LN2 0.693147180559945309417232121458176568 // log e2
5. #define M_LN10 2.30258509299404568401799145468436421 // log e10
6. #define M_PI 3.14159265358979323846264338327950288 // pi
7. #define M_PI_2 1.57079632679489661923132169163975144 // pi/2
8. #define M_PI_4 0.785398163397448309615660845819875721 // pi/4
9. #define M_1_PI 0.318309886183790671537767526745028724 // 1/pi
10. #define M_2_PI 0.636619772367581343075535053490057448 // 2/pi
11. #define M_2_SQRTPI 1.12837916709551257389615890312154517 // 2/sqrt(pi)
12. #define M_SQRT2 1.41421356237309504880168872420969808 // sqrt(2)
13. #define M_SQRT1_2 0.707106781186547524400844362104849039 // 1/sqrt(2)
常用函数：

指数运算
1. NSLog(@"%.f", pow(3,2) ); //result 9
2. NSLog(@"%.f", pow(3,3) ); //result 27
开平方运算（计算两点间的距离时用到）
1. NSLog(@"%.f", sqrt(16) ); //result 4
2. NSLog(@"%.f", sqrt(81) ); //result 9
上舍入
1. NSLog(@"res: %.f", ceil(3.000000000001)); //result 4
2. NSLog(@"res: %.f", ceil(3.00)); //result 3
下舍入
1. NSLog(@"res: %.f", floor(3.000000000001)); //result 3
2. NSLog(@"res: %.f", floor(3.9999999)); //result 3
四舍五入
1. NSLog(@"res: %.f", round(3.5)); //result 4
2. NSLog(@"res: %.f", round(3.46)); //result 3
3. NSLog(@"res: %.f", round(-3.5)); //NB: this one returns -4
最小值
1. NSLog(@"res: %.f", fmin(5,10)); //result 5
最大值
1. NSLog(@"res: %.f", fmax(5,10)); //result 10
绝对值
1. NSLog(@"res: %.f", fabs(10)); //result 10
2. NSLog(@"res: %.f", fabs(-10)); //result 10
NSDate

得到当前的日期
1. NSDate *date = [NSDate date];
日期之间比较可用以下方法
1. - (BOOL)isEqualToDate:(NSDate *)otherDate;// 与otherDate比较，相同返回YES
2. - (NSDate *)earlierDate:(NSDate *)anotherDate;// 与anotherDate比较，返回较早的那个日期
3. - (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
1. NSLog(@”date = %@”,[data description]);
设置日期显示格式
1. NSDateFormatter *formatter =[[[NSDateFormatter alloc] init] autorelease];
2. [formatter setTimeStyle:NSDateFormatterFullStyle]; //设置几种默认的显示效果
3. [formatter setDateFormat:@"yyyy-MM-dd HH:mm:ss a"];//设置自定义的显示效果
4. NSLog([formatter stringFromDate:date]);
NSData
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原文地址：https://www.cnblogs.com/Free-Thinker/p/4941825.html

iOS开发宝典:String用法大全

一、NSString

二、NSMutableString

三、NSArray

四、宏定义#define讲解