Objective-C ,ios,iphone开发基础:几个常用类-NSNumber

2013-08-21

在Objective-C，包括int double float 等等再内的基础数据类型都不是一个类，所以就不能给它们发送消息，也就是说不能调用方法，那怎么办呢 ？Objective-C提供了一个 NSNumber

类来作为一个中转，可以将所有的普通数据类型转化为NSNumber类型，这样就符合Objective-C的消息机制了。

NSNumber 

#import <Foundation/Foundation.h>

int main (int argc, const char * argv[])
{

    @autoreleasepool {
        
        //初始化NSNumber使用格式：  numberWith+object
        NSNumber * intNumber=[NSNumber numberWithInteger:100];
        //跳到NSInter定义的地方可以看到：typedef long NSInteger; NSInteger 其实就是long类型，只不过是重新定义了一个名字罢了。
        // 取intNumber的值使用格式： object+Value
        NSInteger dwint=[intNumber integerValue];
        NSLog(@"%ld",dwint);
    }
    return 0;
}
结果：
2013-08-21 11:42:07.151 NSNumber[492:707] 100

　

#import <Foundation/Foundation.h>

int main (int argc, const char * argv[])
{

    @autoreleasepool {
        
        //  numberWith+object
        NSNumber * intNumber=[NSNumber numberWithDouble:12345e+15];
        NSLog(@"%ld",[intNumber integerValue]);
    }
    return 0;
}

结果：
2013-08-21 11:34:23.631 NSNumber[435:707] -9223372036854775808

#import <Foundation/Foundation.h>

int main (int argc, const char * argv[])
{

    @autoreleasepool {
        
        //  numberWith+object
        NSNumber * intNumber=[NSNumber numberWithDouble:12345e+10];
        NSLog(@"%ld",[intNumber integerValue]);
    }
    return 0;
}

结果：

2013-08-21 11:36:19.330 NSNumber[451:707] 123450000000000

给已经初始化的NSNumber对象重新赋值，也就是改变他指向空间里面的内容，只能通过给他重新指向来改变它的值，不能改变它最开始指向空间里面的值，因为产生的是一个常量，

#import <Foundation/Foundation.h>

int main (int argc, const char * argv[])
{

    @autoreleasepool {
        
        NSNumber * intNumber=[NSNumber numberWithInteger:100];
        NSInteger dwint=[intNumber integerValue];
        NSLog(@"%ld",dwint);
        //NSLog(@"%d",[intNumber retainCount]); const
        //[intNumber initWithInteger:100];  error  ，cannot be sent to an abstract object of class 
        intNumber=[NSNumber numberWithInteger:1000];
        NSLog(@"%ld",[intNumber integerValue]);
    }
    return 0;
}
结果：

2013-08-21 13:43:39.382 NSNumber[556:707] 100
2013-08-21 13:43:39.389 NSNumber[556:707] 1000

附上NSNumber类的原型：

/*    NSValue.h
    Copyright (c) 1994-2011, Apple Inc. All rights reserved.
*/

#import <Foundation/NSObject.h>

@class NSString, NSDictionary;

@interface NSValue : NSObject <NSCopying, NSCoding>

- (void)getValue:(void *)value;
- (const char *)objCType;

@end

@interface NSValue (NSValueCreation)

- (id)initWithBytes:(const void *)value objCType:(const char *)type;
+ (NSValue *)valueWithBytes:(const void *)value objCType:(const char *)type;
+ (NSValue *)value:(const void *)value withObjCType:(const char *)type;

@end

@interface NSValue (NSValueExtensionMethods)

+ (NSValue *)valueWithNonretainedObject:(id)anObject;
- (id)nonretainedObjectValue;

+ (NSValue *)valueWithPointer:(const void *)pointer;
- (void *)pointerValue;

- (BOOL)isEqualToValue:(NSValue *)value;

@end

//开始================================================================================
@interface NSNumber : NSValue

- (char)charValue;
- (unsigned char)unsignedCharValue;
- (short)shortValue;
- (unsigned short)unsignedShortValue;
- (int)intValue;
- (unsigned int)unsignedIntValue;
- (long)longValue;
- (unsigned long)unsignedLongValue;
- (long long)longLongValue;
- (unsigned long long)unsignedLongLongValue;
- (float)floatValue;
- (double)doubleValue;
- (BOOL)boolValue;
- (NSInteger)integerValue NS_AVAILABLE(10_5, 2_0);
- (NSUInteger)unsignedIntegerValue NS_AVAILABLE(10_5, 2_0);

- (NSString *)stringValue;

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

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

- (NSString *)descriptionWithLocale:(id)locale;

@end

@interface NSNumber (NSNumberCreation)

- (id)initWithChar:(char)value;
- (id)initWithUnsignedChar:(unsigned char)value;
- (id)initWithShort:(short)value;
- (id)initWithUnsignedShort:(unsigned short)value;
- (id)initWithInt:(int)value;
- (id)initWithUnsignedInt:(unsigned int)value;
- (id)initWithLong:(long)value;
- (id)initWithUnsignedLong:(unsigned long)value;
- (id)initWithLongLong:(long long)value;
- (id)initWithUnsignedLongLong:(unsigned long long)value;
- (id)initWithFloat:(float)value;
- (id)initWithDouble:(double)value;
- (id)initWithBool:(BOOL)value;
- (id)initWithInteger:(NSInteger)value NS_AVAILABLE(10_5, 2_0);
- (id)initWithUnsignedInteger:(NSUInteger)value NS_AVAILABLE(10_5, 2_0);

+ (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);

@end