OC的开始（一）之----HelloWord与类的创建及使用

这里说一下重写的父类description方法：当我们不重写这个方法的时候，直接打印出得结果是对象，看代码：

        // 声明多个Person对象Person *p1 = [Person personWithName:@"zhangsan" number:10001 age:26 score:90.5];Person *p2 = [Person personWithName:@"lisi" number:10002 age:22 score:91.5];Person *p3 = [Person personWithName:@"wangwu" number:10004 age:24 score:90.5];Person *p4 = [Person personWithName:@"zhaoliu" number:10003 age:25 score:92.5];Person *p5 = [Person personWithName:@"xiaoqi" number:10008 age:26 score:96.5];Person *p6 = [Person personWithName:@"bazai" number:10006 age:27 score:93.5];Person *p7 = [Person personWithName:@"xiaojiu" number:10005 age:21 score:92.5];Person *p8 = [Person personWithName:@"shidi" number:10007 age:18 score:99.5];// 声明一个不可变数组NSArray *persons = [NSArray arrayWithObjects:p1, p2, p3, p4, p5, p6, p7, p8, nil];NSLog(@"%@", persons);

2015-05-22 15:31:47.320 Test02[1653:116214] ("<Person: 0x100200f80>","<Person: 0x100201270>","<Person: 0x1002012e0>","<Person: 0x100201350>","<Person: 0x1002013c0>","<Person: 0x100201430>","<Person: 0x1002014a0>","<Person: 0x100201510>"
)

这样执行的的显示结果是每一个元素对象在堆内存中站得地址，那么我们看看把description重写后再次打印的结果：

在Person.m文件中重写description方法

- (NSString *)description
{return [NSString stringWithFormat:@"name = %@ number = %ld age = %ld score = %.2f", _name, _number, _age, _score];
}

然后打印结果：

2015-05-22 15:35:00.174 Test02[1669:117516] ("name = zhangsan number = 10001 age = 26 score = 90.50","name = lisi number = 10002 age = 22 score = 91.50","name = wangwu number = 10004 age = 24 score = 90.50","name = zhaoliu number = 10003 age = 25 score = 92.50","name = xiaoqi number = 10008 age = 26 score = 96.50","name = bazai number = 10006 age = 27 score = 93.50","name = xiaojiu number = 10005 age = 21 score = 92.50","name = shidi number = 10007 age = 18 score = 99.50"
)

很明显，当我们直接打印数组的时候，系统调用了父类的description方法。

现在开始我们的排序之旅：

一、使用冒泡排序：

        // 定义一个可变数组，将persons的值赋给可变数组NSMutableArray *muPersons = [NSMutableArray arrayWithArray:persons];// 使用冒泡按照number进行升序排序for (int i = 0; i < muPersons.count - 1; i++) {for (int j = 0; j < muPersons.count - 1 - i; j++) {// 前一个元素的number属性大于后一个元素的number属性时 两个元素交换位置if ([muPersons[j] number] > [muPersons[j + 1] number]) {[muPersons exchangeObjectAtIndex:j withObjectAtIndex:j + 1];}}}NSLog(@"%@", muPersons);

查看结果：

2015-05-22 15:50:26.322 Test02[1719:122150] ("name = zhangsan number = 10001 age = 26 score = 90.50","name = lisi number = 10002 age = 22 score = 91.50","name = zhaoliu number = 10003 age = 25 score = 92.50","name = wangwu number = 10004 age = 24 score = 90.50","name = xiaojiu number = 10005 age = 21 score = 92.50","name = bazai number = 10006 age = 27 score = 93.50","name = shidi number = 10007 age = 18 score = 99.50","name = xiaoqi number = 10008 age = 26 score = 96.50"
)

二、使用sortedArrayUsingSelector排序：

使用sortedArrayUsingSelector之前，需要我们在person中写专门写一个排序的方法供sortedArrayUsingSelector使用。

在person.h文件中自定义排序方法compareSortNumber:

// 自定义排序方法
- (NSComparisonResult)compareSortNumber:(Person *)person;

在person.m文件中实现排序：

// 自定义排序方法
- (NSComparisonResult)compareSortNumber:(Person *)person
{if ([self number] > [person number]) {return NSOrderedDescending;}return NSOrderedSame;
}

在main.m文件中调用sortedArrayUsingSelector对number进行升序排列

        // 使用sortedArrayUsingSelector对number进行升序排列NSArray *selArray = [persons sortedArrayUsingSelector:@selector(compareSortNumber:)];NSLog(@"%@", selArray);

运行结果：

2015-05-22 16:33:49.996 Test02[1927:136447] ("name = zhangsan number = 10001 age = 26 score = 90.50","name = lisi number = 10002 age = 22 score = 91.50","name = zhaoliu number = 10003 age = 25 score = 92.50","name = wangwu number = 10004 age = 24 score = 90.50","name = xiaojiu number = 10005 age = 21 score = 92.50","name = bazai number = 10006 age = 27 score = 93.50","name = shidi number = 10007 age = 18 score = 99.50","name = xiaoqi number = 10008 age = 26 score = 96.50"
)

三、使用sortedArrayUsingComparator对number进行升序排列

        // 使用sortedArrayUsingComparator对number进行升序排列NSArray *comArray = [persons sortedArrayUsingComparator:^NSComparisonResult(id obj1, id obj2) {Person *p1 = obj1;Person *p2 = obj2;if ([p1 number] > [p2 number]) {return NSOrderedDescending;}return NSOrderedSame;}];NSLog(@"%@", comArray);

运行结果：

2015-05-22 17:02:44.189 Test02[2039:148253] ("name = zhangsan number = 10001 age = 26 score = 90.50","name = lisi number = 10002 age = 22 score = 91.50","name = zhaoliu number = 10003 age = 25 score = 92.50","name = wangwu number = 10004 age = 24 score = 90.50","name = xiaojiu number = 10005 age = 21 score = 92.50","name = bazai number = 10006 age = 27 score = 93.50","name = shidi number = 10007 age = 18 score = 99.50","name = xiaoqi number = 10008 age = 26 score = 96.50"
)

总结：

使用冒泡排序的时候我们需要重新定义可变数组对数组中的元素进行排序，sortedArrayUsingSelector排序我们需要写单独写一个方法给sortedArrayUsingSelector调用，太麻烦了，最后一种方法是OC中最常用的排序方法。

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