public class NSValue : NSObject, NSCopying, NSSecureCoding

• 将任意数据类型包装成对象。

1、比较两个 NSValue 类型数据的大小

	let value1:NSValue = NSValue(point: NSMakePoint(10, 32))
	let value2:NSValue = NSValue(point: NSMakePoint(10, 32))
	    
	let bl1:Bool = value1 == value2
	    
	let bl2:Bool = value1.isEqualToValue(value2)

2、NSValue 与 OC 数据类型的相互转换

	// OC 转 NSValue
	let value:NSValue = NSValue(point: NSMakePoint(10, 32))
		
	// NSValue 转 OC
	let point:NSPoint = value.pointValue