首先看一个问题如下：

把一些数（int ,BOOL类型等）封装到NSNumber对象中，而这些NSNumber类型的数据再放到一个字典当中，循环字典，取出每一个NSNumber类型的对象，如何才能够知道NSNumber对象中放的是什么类型的数（int ，BOOL类型等）？

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NSDictionary *dic = [NSDictionary dictionaryWithObjectsAndKeys:[NSNumber numberWithBool:YES],@"key1",

            [NSNumber numberWithDouble:1.00f],@"key2",[NSNumber numberWithInt:1],@"key3",[NSNumber

             numberWithFloat:33.0f], @"key4", nil]; 

 for(NSString *key in dic){ 

        id value = [dic valueForKey:key]; 

        if([value isKindOfClass:[NSNumber class]]){ 

            constchar * pObjCType = [((NSNumber*)value) objCType]; 

            if (strcmp(pObjCType, @encode(int))  == 0) { 

                NSLog(@"字典中key=%@的值是int类型,值为%d",key,[value intValue]); 

            } 

            if (strcmp(pObjCType, @encode(float)) == 0) { 

                NSLog(@"字典中key=%@的值是float类型,值为%f",key,[value floatValue]); 

            } 

            if (strcmp(pObjCType, @encode(double))  == 0) { 

                NSLog(@"字典中key=%@的值是double类型,值为%f",key,[value doubleValue]); 

            } 

            if (strcmp(pObjCType, @encode(BOOL)) == 0) { 

                NSLog(@"字典中key=%@的值是bool类型,值为%i",key,[value boolValue]); 

            } 

        } 

    }