NSNumber

//1.数值对象类型 NSNumber
NSNumber * num1 = @123;//对象，NSNumber 常量
NSNumber * num2 = @123.45;//对象可以存入OC的数组

NSLog(@"num1=%@,num2=%@",num1,num2);//必须使用@打印对象

//2.使用NSNumber构造器
NSNumber * num3 = [NSNumber numberWithInt:234];//通过int构造NSNumber
NSNumber * num4 = [NSNumber numberWithChar:'d'];

NSLog(@"num3=%@,num4=%@",num3,num4);

//3.@字符串的使用 @（数值表达式）把数值转换成对象
int a1 = 45;
int a2 = 345;

NSNumber * num6 = @(a1);
NSNumber * num7 = @(123);//或者@123
NSNumber * num8 = @(a1 + a2);

NSLog(@"num6=%@,num7=%@,num8=%@",num6,num7,num8);

//4.把NSNumber类型转换成普通数字类型
NSNumber * num9 = [NSNumber numberWithFloat:3.14];
NSNumber * num10 = @123;

NSLog(@"num9=%@,num10=%@",num9,num10);
NSLog(@"num9=%g,num10=%d",num9.floatValue,num10.intValue);