struct 转对象（NSValue）

1.struct aStruct{    int a;    int b;};typedef struct aStruct aStruct;

2.aStruct struct; struct.a = 0; struct.b = 0;
NSValue *anObj = [NSValue value:&struct withObjCType:@encode(aStruct)];NSArray *array = [NSArray arrayWithObjects:anObj, nil];
3.
NSValue *anObj = [array objectAtIndex:0];aStruct struct;[anObj getValue:&struct];