NSNumber
- NSNumber 是一個類。OC中提供了NSNumber類來將基本數據類型“包裝”成數字對象，這樣我們就可以將基本數據類型當做對象來處理。同樣也可以將包裝后的對象還原成基本數據類型。
NSNumber的類方法
+ (NSNumber *)numberWithChar:(char)value;
+ (NSNumber *)numberWithUnsignedChar:(unsigned char)value;
+ (NSNumber *)numberWithShort:(short)value;
+ (NSNumber *)numberWithUnsignedShort:(unsigned short)value;
+ (NSNumber *)numberWithInt:(int)value;
+ (NSNumber *)numberWithUnsignedInt:(unsigned int)value;
+ (NSNumber *)numberWithLong:(long)value;
+ (NSNumber *)numberWithUnsignedLong:(unsigned long)value;
+ (NSNumber *)numberWithLongLong:(long long)value;
+ (NSNumber *)numberWithUnsignedLongLong:(unsigned long long)value;
+ (NSNumber *)numberWithFloat:(float)value;
+ (NSNumber *)numberWithDouble:(double)value;
+ (NSNumber *)numberWithBool:(BOOL)value;
+ (NSNumber *)numberWithInteger:(NSInteger)value NS_AVAILABLE(10_5, 2_0);
+ (NSNumber *)numberWithUnsignedInteger:(NSUInteger)value NS_AVAILABLE(10_5, 2_0);
NSNumber的實例方法
//實例方法 初始化
- (NSNumber *)initWithChar:(char)value NS_DESIGNATED_INITIALIZER;
- (NSNumber *)initWithUnsignedChar:(unsigned char)value NS_DESIGNATED_INITIALIZER;
- (NSNumber *)initWithShort:(short)value NS_DESIGNATED_INITIALIZER;
- (NSNumber *)initWithUnsignedShort:(unsigned short)value NS_DESIGNATED_INITIALIZER;
- (NSNumber *)initWithInt:(int)value NS_DESIGNATED_INITIALIZER;
- (NSNumber *)initWithUnsignedInt:(unsigned int)value NS_DESIGNATED_INITIALIZER;
- (NSNumber *)initWithLong:(long)value NS_DESIGNATED_INITIALIZER;
- (NSNumber *)initWithUnsignedLong:(unsigned long)value NS_DESIGNATED_INITIALIZER;
- (NSNumber *)initWithLongLong:(long long)value NS_DESIGNATED_INITIALIZER;
- (NSNumber *)initWithUnsignedLongLong:(unsigned long long)value NS_DESIGNATED_INITIALIZER;
- (NSNumber *)initWithFloat:(float)value NS_DESIGNATED_INITIALIZER;
- (NSNumber *)initWithDouble:(double)value NS_DESIGNATED_INITIALIZER;
- (NSNumber *)initWithBool:(BOOL)value NS_DESIGNATED_INITIALIZER;
- (NSNumber *)initWithInteger:(NSInteger)value NS_AVAILABLE(10_5, 2_0) NS_DESIGNATED_INITIALIZER;
- (NSNumber *)initWithUnsignedInteger:(NSUInteger)value NS_AVAILABLE(10_5, 2_0) NS_DESIGNATED_INITIALIZER;
- 使用 @(someThing);// 快速裝箱，自動判斷類型。
NSNumber *number = @(1);
將基本類型數據封裝到NSNumber中后，通過下面的實例方法重新獲取它
NSNumber *myNumber = [NSNumber numberWithLong:0xabcdef];
NSNumber *floatnumber = [NSNumber numberWithFloat:12.33];
NSNumber *intNumber = [NSNumber numberWithInt:100];
NSNumber *doublenumber = [NSNumber numberWithDouble:12345e+15];
NSNumber *charNumber = [NSNumber numberWithChar:'X'];
int myInt = [intNumber intValue];
float myFloat = [floatnumber floatValue];
double myDouble = [doublenumber doubleValue];
char myChar = [charNumber charValue]；
- 因為OC的集合當中存儲的數據必須是OC對象。舉個例子
NSMutableArray *myArray = [[NSMutableArray alloc] init ];
[myArray addObject: 6 ];
上面的寫法編譯器會報錯。解決方法就是把'6'包裝成一個NSNumber對象。
NSMutableArray *myArray = [[NSMutableArray alloc] init ];
[myArray addObject:[NSNumber numberWithInt:6] ];
NSLog(@"array content is %@", myArray);
- NSNumber轉成NSString類型
// 下面 A是NSNumber類型 B是NSString類型
NSNumberFormatter *numberFormatter = [[NSNumberFormatter alloc] init];
B = [numberFormatter stringFromNumber:A];
- 用NSNumber排序
NSNumber *number1 = [NSNumber numberWithInteger:13];
NSNumber *number2 = [NSNumber numberWithInteger:14];
NSComparisonResult result = [number1 compare:number2];
if (result == NSOrderedAscending) {
NSLog(@"升序");//number2 比 number1 大
}else if (result == NSOrderedSame){
NSLog(@"一致");
}else if (result == NSOrderedDescending){
NSLog(@"降序");
}else{
NSLog(@"error");
}
- 用NSNumber判斷是否一致
NSNumber *number1 = [NSNumber numberWithInteger:13];
NSNumber *number2 = [NSNumber numberWithInteger:14];
if ([number1 isEqualToNumber:number2]) {
NSLog(@"same");
}else{
NSLog(@"nonono");
}
int、NSInteger、NSUInteger、NSNumber之間的區別和聯系
- int ： 當使用int類型定義變量的時候，可以像寫C程序一樣去使用。當你不知道程序運行在哪種處理器架構時，你最好使用NSInteger，因為在有可能int在32位系統中只是int類型，而在64位系統，int可能變成long型。除非不得不使用int／long型，否則推薦使用NSInteger。
- NSInteger/NSUInteger是一種動態定義的類型，在不同的設備，不同的架構，有可能是int類型，有可能是long類型。NSUInteger是無符號的，即沒有負數，NSInteger是有符號的。
- NSInteger是基礎類型，NSNumber是一個類，如果需要存儲一個數值，直接使用NSInteger是不行的，因為OC的集合當中存儲的數據必須是OC對象。
