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：
1 /* NSValue.h 2 Copyright (c) 1994-2011, Apple Inc. All rights reserved. 3 */ 4 5 #import <Foundation/NSObject.h> 6 7 @class NSString, NSDictionary; 8 9 @interface NSValue : NSObject <NSCopying, NSCoding> 10 11 - (void)getValue:(void *)value; 12 - (const char *)objCType; 13 14 @end 15 16 @interface NSValue (NSValueCreation) 17 18 - (id)initWithBytes:(const void *)value objCType:(const char *)type; 19 + (NSValue *)valueWithBytes:(const void *)value objCType:(const char *)type; 20 + (NSValue *)value:(const void *)value withObjCType:(const char *)type; 21 22 @end 23 24 @interface NSValue (NSValueExtensionMethods) 25 26 + (NSValue *)valueWithNonretainedObject:(id)anObject; 27 - (id)nonretainedObjectValue; 28 29 + (NSValue *)valueWithPointer:(const void *)pointer; 30 - (void *)pointerValue; 31 32 - (BOOL)isEqualToValue:(NSValue *)value; 33 34 @end 35 //开始================================================================================ 36 @interface NSNumber : NSValue 37 38 - (char)charValue; 39 - (unsigned char)unsignedCharValue; 40 - (short)shortValue; 41 - (unsigned short)unsignedShortValue; 42 - (int)intValue; 43 - (unsigned int)unsignedIntValue; 44 - (long)longValue; 45 - (unsigned long)unsignedLongValue; 46 - (long long)longLongValue; 47 - (unsigned long long)unsignedLongLongValue; 48 - (float)floatValue; 49 - (double)doubleValue; 50 - (BOOL)boolValue; 51 - (NSInteger)integerValue NS_AVAILABLE(10_5, 2_0); 52 - (NSUInteger)unsignedIntegerValue NS_AVAILABLE(10_5, 2_0); 53 54 - (NSString *)stringValue; 55 56 - (NSComparisonResult)compare:(NSNumber *)otherNumber; 57 58 - (BOOL)isEqualToNumber:(NSNumber *)number; 59 60 - (NSString *)descriptionWithLocale:(id)locale; 61 62 @end 63 64 @interface NSNumber (NSNumberCreation) 65 66 - (id)initWithChar:(char)value; 67 - (id)initWithUnsignedChar:(unsigned char)value; 68 - (id)initWithShort:(short)value; 69 - (id)initWithUnsignedShort:(unsigned short)value; 70 - (id)initWithInt:(int)value; 71 - (id)initWithUnsignedInt:(unsigned int)value; 72 - (id)initWithLong:(long)value; 73 - (id)initWithUnsignedLong:(unsigned long)value; 74 - (id)initWithLongLong:(long long)value; 75 - (id)initWithUnsignedLongLong:(unsigned long long)value; 76 - (id)initWithFloat:(float)value; 77 - (id)initWithDouble:(double)value; 78 - (id)initWithBool:(BOOL)value; 79 - (id)initWithInteger:(NSInteger)value NS_AVAILABLE(10_5, 2_0); 80 - (id)initWithUnsignedInteger:(NSUInteger)value NS_AVAILABLE(10_5, 2_0); 81 82 + (NSNumber *)numberWithChar:(char)value; 83 + (NSNumber *)numberWithUnsignedChar:(unsigned char)value; 84 + (NSNumber *)numberWithShort:(short)value; 85 + (NSNumber *)numberWithUnsignedShort:(unsigned short)value; 86 + (NSNumber *)numberWithInt:(int)value; 87 + (NSNumber *)numberWithUnsignedInt:(unsigned int)value; 88 + (NSNumber *)numberWithLong:(long)value; 89 + (NSNumber *)numberWithUnsignedLong:(unsigned long)value; 90 + (NSNumber *)numberWithLongLong:(long long)value; 91 + (NSNumber *)numberWithUnsignedLongLong:(unsigned long long)value; 92 + (NSNumber *)numberWithFloat:(float)value; 93 + (NSNumber *)numberWithDouble:(double)value; 94 + (NSNumber *)numberWithBool:(BOOL)value; 95 + (NSNumber *)numberWithInteger:(NSInteger)value NS_AVAILABLE(10_5, 2_0); 96 + (NSNumber *)numberWithUnsignedInteger:(NSUInteger)value NS_AVAILABLE(10_5, 2_0); 97 98 @end
作者：wsq724439564 发表于2013-8-21 13:55:49 原文链接
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