OC-NSNumber and NSValue are generally used for boxing and unboxing

NSNumber

装箱：将值类型转换成引用类型
拆箱：将引用类型转换成值类型
int a = 1; This is the value type It should be some default type
string a;或者NSNumberThis is the reference type Should be able to say yesNSObject

装箱

NSNumber *num1 = [[NSNumber alloc]initWithInt:20];
NSLog(@"%@ %@",num1,[num1 class]);//20 __NSCFNumber


NSNumber *num2 = [[NSNumber alloc]initWithChar:'a'];
NSLog(@"%@",num2);//97 This is to convert the letters into ascll码


NSNumber *num3 = @300;
NSLog(@"%@",num3);//300


int a = 29;
NSNumber *num5 = @(a);
NSLog(@"%@",num5);//5

拆箱

通过intValue floatValue拆箱

NSNumber *num3 = @300;
NSLog(@“%d”,num3 intValue);//300
NSNumber *num3 = @300.0;
NSLog(@“%f”,num3 floatValue);//300.0

NSValue(I don't understand)

typedef struct 
{
    
	int age;
	char* name;
	chat sex;
} SPerson
Sperson p;
p.name = "Yang";
p.age = 10;
p.sex = 'w';

//Convert a struct toNSValue对象
NSValue* value = [NSValue valueWithBytes:&p objCType:@encode(SPerson)];
SPerson p2;
//将一个NSValueObjects are converted to structs
[value getValue:&p2];

NSLog(@"%s",p2.name);
NSLog(@"%d",p2.age);
NSLog(@"%c",p2.sex);

NSRange range = {
    12,2};
//Commonly used structure packing
NSValue *rvalue = [NSValue valueWithRange:range];
//rangeValue将NSRange拆箱
NSLog(@"%@",NSStringFromRange([rvalue rangeValue]));