Objective-C学习笔记-NSNumber与NSInteger

1.由于Objective-C是C的超集，所以C支持的基本数据类型，OC也支持，而NSNumber就是对这些基本数据类型的封装，例如char，short，int，float

2.NSNumber可以通过下面两种方法初始化

NSNumber n=[NSNumber numberWithInteger:100];
NSNumber k=[[NSNumber alloc] initWithInt:999];

 其他数据类型还有

+ (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 *)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;

3.NSNumber不支持加减乘除，如果需要做这些运算，可以使用它们的属性

@property (readonly) char charValue;
@property (readonly) unsigned char unsignedCharValue;
@property (readonly) short shortValue;
@property (readonly) unsigned short unsignedShortValue;
@property (readonly) int intValue;
@property (readonly) unsigned int unsignedIntValue;
@property (readonly) long longValue;
@property (readonly) unsigned long unsignedLongValue;
@property (readonly) long long longLongValue;
@property (readonly) unsigned long long unsignedLongLongValue;
@property (readonly) float floatValue;
@property (readonly) double doubleValue;
@property (readonly) BOOL boolValue;

4.NSNumber常用方法有两个

• isEqualToNumber，和另外一个NSNumber比较，相同则返回true，不相同返回false
• compare，和另外一个NSNumber比较，返回值是一个枚举类型，NSOrderedAscending(小) NSOrderedSame(相等)NSOrderedDescending(大)

- (BOOL)isEqualToNumber:(NSNumber *)number;

- (NSComparisonResult)compare:(NSNumber *)otherNumber;

5.还会经常用到的类型有NSUInteger和NSInteger，不要以为前面带上了NS就是类，其实这两个是使用typedef对基本类型的一个新定义

#if __LP64__ || (TARGET_OS_EMBEDDED && !TARGET_OS_IPHONE) || TARGET_OS_WIN32 || NS_BUILD_32_LIKE_64
typedef long NSInteger;
typedef unsigned long NSUInteger;
#else
typedef int NSInteger;
typedef unsigned int NSUInteger;
#endif