即copy 与 mutablecopy，浅拷贝拷贝指针，深拷贝拷贝才是拷贝对象，copy是不可变的拷贝，mutablecopy是可变拷贝
NSString *str = [NSString stringWithFormat:@"hello"];
NSString *str1 = [str copy];
NSMutableString *str2 = [str mutableCopy];
[str2 appendString:@"world"];
NSLog(@"%p %p %p",str,str1,str2);
NSLog(@"%@ %@ %@",str,str1,str2);
copy过后得到对象为不可变类型，mutablecopy过后得到结果是可变类型
不可变类型进行不可变拷贝浅拷贝，其余都是深拷贝
上面规则仅仅限于系统遵循NSCopying协议以及NSMutableCopying协议
也就是NSString NSArray NSDictionary NSSet以及其子类
对象想要进行不可变拷贝需要实现NSCopying协议
对象想要进行可变拷贝需要实现NSMutableCopying协议
@interface People : NSObject
@property (nonatomic,strong) NSString *name;
@end
@implementation People
- (id)copyWithZone:(NSZone *)zone{
//self代表拷贝前的对象
NSLog(@"copyWithZone:%p",self);
/*
直接返回self是浅拷贝
但是大家一般不这么做，因为毫无意义
*/
// return self;
People *people = [[People alloc] init];
people.name = self.name;
return people;
}
- (id)mutableCopyWithZone:(NSZone *)zone{
People *people = [[People alloc] init];
people.name = self.name;
return people;
}
@end
People *people = [[People alloc] init];
people.name = @"张三";
People *people1 = [people mutableCopy];
people.name = @"李四";
NSLog(@"%p %p",people,people1);
NSLog(@"%@ %@",people.name,people1.name);
OC中的谓词操作是针对于数组类型的，他就好比数据库中的查询操作，数据源就是数组，这样的好处是我们不需要编写很多代码就可以去操作数组，同时也起到过滤的作用，我们可以编写简单的谓词语句，就可以从数组中过滤出我们想要的数据。非常方便
People *people = [[People alloc] init];
people.name = @"张三";
people.age = 21;
People *people1 = [[People alloc] init];
people1.name = @"张四";
people1.age = 12;
People *people2 = [[People alloc] init];
people2.name = @"三张";
people2.age = 15;
People *people3 = [[People alloc] init];
people3.name = @"李四";
people3.age = 7;
NSArray *arr = @[people,people1,people2,people3];
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"name like '*张*' and age > 20"];
NSArray *arr1 = [arr filteredArrayUsingPredicate:predicate];
// for (People *people in arr1) {
// NSLog(@"%@ %d",people.name,people.age);
// }
NSArray *arr2 = [arr sortedArrayUsingComparator:^NSComparisonResult(id obj1, id obj2) {
People *p1 = obj1;
People *p2 = obj2;
if (p1.age < p2.age) {
return NSOrderedAscending;
}else{
return NSOrderedDescending;
}
}];
for (People *people in arr2) {
NSLog(@"%@ %d",people.name,people.age);
}