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NSValue类是OC中用来存储任意值的容器，是NSNumber的父类，NSNumber类是用来封装基本数据类型的
初始化方法：
- (instancetype)initWithBytes:(const void *)value
objCType:(const char *)type
//便利构造器方法
+ (NSValue *) valueWithBytes:(const void *)value
objCType:(const char *)type
第一个参数为要封装的变量的地址，第二个参数用来描述该数据类型的字符串，可以用@encode编译器指令自动生成该字符串
用法：
//自定义结构体类型Student
typedef struct student{
char name[50];
char sex[2];
NSInteger age;
NSInteger grade;
char number[50];
}Student;
//创建结构体stu
Student stu = {"smithjackyson","男",23,98,"3112006304"};
//创建NSValue实例value存储stu
NSValue *value = [[NSValue alloc] initWithBytes:&stu objCType:@encode(Student)];
NSValue *value1 = [NSValue valueWithBytes:&stu objCType:@encode(Student)];
获取value中存储的对象如下:
//定义一个新结构体变量stu1 Student stu1; //将value中存储的结构体赋值给stu1 [value getValue:&stu1];
判断两个NSvalue存储的对象是否相同
- (BOOL)isEqualToValue:(NSValue *)aValue
存储各种类型的便利构造器和属性,以及获取对应值的方法:
+ (NSValue *)valueWithRange:(NSRange)range @property(readonly) NSRange rangeValue + (NSValue *)valueWithCGPoint:(CGPoint)point - (CGPoint)CGPointValue + (NSValue *)valueWithCGVector:(CGVector)vector - (CGVector)CGVectorValue + (NSValue *)valueWithCGSize:(CGSize)size - (CGSize)CGSizeValue + (NSValue *)valueWithCGRect:(CGRect)rect - (CGRect)CGRectValue + (NSValue *)valueWithPointer:(const void *)aPointer @property(readonly) void *pointerValue + (NSValue *)valueWithNonretainedObject:(id)anObject @property(readonly) id nonretainedObjectValue + (NSValue *)valueWithCGAffineTransform:(CGAffineTransform)transform - (CGAffineTransform)CGAffineTransformValue + (NSValue *)valueWithUIEdgeInsets:(UIEdgeInsets)insets - (UIEdgeInsets)UIEdgeInsetsValue + (NSValue *)valueWithUIOffset:(UIOffset)insets - (UIOffset)UIOffsetValue + (NSValue *)valueWithCATransform3D:(CATransform3D)aTransform @property(readonly) CATransform3D CATransform3DValue + (NSValue *)valueWithCMTime:(CMTime)time @property(readonly) CMTime CMTimeValue + (NSValue *)valueWithCMTimeRange:(CMTimeRange)timeRange @property(readonly) CMTimeRange CMTimeRangeValue + (NSValue *)valueWithCMTimeMapping:(CMTimeMapping)timeMapping @property(readonly) CMTimeMapping CMTimeMappingValue + (NSValue *)valueWithMKCoordinate:(CLLocationCoordinate2D)coordinate @property(readonly) CLLocationCoordinate2D MKCoordinateValue + (NSValue *)valueWithMKCoordinateSpan:(MKCoordinateSpan)span @property(readonly) MKCoordinateSpan MKCoordinateSpanValue + (NSValue *)valueWithSCNVector3:(SCNVector3)vector @property(nonatomic, readonly) SCNVector3 SCNVector3Value + (NSValue *)valueWithSCNVector4:(SCNVector4)vector @property(nonatomic, readonly) SCNVector4 SCNVector4Value + (NSValue *)valueWithSCNMatrix4:(SCNMatrix4) @property(nonatomic, readonly) SCNMatrix4 SCNMatrix4Value
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原文地址：http://www.cnblogs.com/smithjackyson/p/5059250.html
