数组 基本用法和排序

1.创建数组

[objc] view
plaincopy1. // 创建一个空的数组

2. NSArray *array = [NSArray array];
3. // 创建有1个元素的数组
4. array = [NSArray arrayWithObject:@”123”];
5. // 创建有多个元素的数组
6. array = [NSArray arrayWithObjects:@”a”, @”b”, @”c”, nil nil];
7. NSArray *array3 = [array arrayByAddingObjectsFromArray:[NSArray arrayWithObjects:@”4”, @”5”, nil nil]];
9. NSArray *array4 = [NSArray arrayWithObjects:@”1”, @”2”, @”3”, @”4”, nil nil];
10. NSRange range = NSMakeRange(1, 2);
11. NSArray *array5 = [array4 subarrayWithRange:range];

2.数组的一些基本方法

[objc] view
plaincopy1. int count = [array count];//个数

2. // 判断是否包含了某个元素
3. if ([array containsObject:@”a”]) {
4. NSLog(@”包含了字符串a”);
5. }
6. NSString *last = [array lastObject];最后一个元素
7. NSString *str = [array objectAtIndex:1];根据索引获取数组中的元素
8. int index = [array indexOfObject:@”c”];获取指定元素的索引
9. // 让数组里面的所有对象都调用test方法，123为参数
10. NSArray *array = [NSArray arrayWithObjects:stu1, stu2, stu3, nil nil];
11. [array makeObjectsPerformSelector:@selector(test2:) withObject:@”123”];
12. NSArray *array = [NSArray arrayWithObjects:@”1”, @”2”, @”3”, @”4”, nil nil];
13. // 1-2-3-4
14. // 利用分隔符-拼接所有的数组元素
15. NSString *str = [array componentsJoinedByString:@”-“];
16. // 将一个数组写入文件（生成的是一个xml文件）
17. NSString *path = @”/Users/apple/Desktop/array.xml”;
18. [array writeToFile:path atomically:YES];
19. path = @”/Users/apple/Desktop/array.txt”;
20. // 从文件中读取数组内容（文件有严格的格式要求）
21. NSArray *array2 = [NSArray arrayWithContentsOfFile:path];

3.遍历数组

[objc] view
plaincopy1. #pragma mark 遍历数组1

2. void arrayFor1() {
3. NSArray *array = [NSArray arrayWithObjects:stu1, @”1”, @”2”, @”3”, nil nil];
4. int count = array.count;
5. for (int i = 0; i<count; i++) {
6. id obj = [array objectAtIndex:i];
7. }
8. }
10. #pragma mark 遍历数组2 快速遍历
11. void arrayFor2() {
12. Student *stu1 = [Student student];
13. NSArray *array = [NSArray arrayWithObjects:stu1, @”1”, @”2”, @”3”, nil nil];
14. int i =0;
15. for (id obj in array) {
16. NSLog(@”%i-%@”, i, obj);
17. i++;
18. }
19. }
21. #pragma mark 遍历数组3
22. void arrayFor3() {
23. Student *stu1 = [Student student];
24. NSArray *array = [NSArray arrayWithObjects:stu1, @”1”, @”2”, @”3”, nil nil];
25. [array enumerateObjectsUsingBlock:
26. ^(id obj, NSUInteger idx, BOOLBOOL *stop) {
27. NSLog(@”%i-%@”, idx, obj);
28. // 如果索引为1，就停止遍历
29. if (idx == 1) {
30. // 利用指针修改外面BOOL变量的值
31. *stop = YES;
32. }
33. }];
34. }
36. #pragma mark 遍历数组4
37. void arrayFor4() {
38. Student *stu1 = [Student student];
39. NSArray *array = [NSArray arrayWithObjects:stu1, @”1”, @”2”, @”3”, nil nil];
40. // 获取数组的迭代器
41. // NSEnumerator *enumerator = [array objectEnumerator];
42. // 反序迭代器（从尾部开始遍历元素）
43. NSEnumerator *enumerator = [array reverseObjectEnumerator];
44. // allObjects是取出没有被遍历过的对象
45. NSArray *array2 = [enumerator allObjects];
46. NSLog(@”array2:%@”, array2);
47. // 获取下一个需要遍历的元素
48. id obj = nil;
49. while (obj = [enumerator nextObject]) {
50. NSLog(@”obj=%@”, obj);
51. }
52. }

4.数组排序

[objc] view
plaincopy1. #pragma mark 数组排序1

2. void arraySort1() {
3. NSArray *array = [NSArray arrayWithObjects:@”2”, @”3”, @”1”, @”4”, nil nil];
5. // 返回一个排好序的数组，原来数组的元素顺序不会改变
6. // 指定元素的比较方法：compare:
7. NSArray *array2 = [array sortedArrayUsingSelector:@selector(compare:)];
8. NSLog(@”array2:%@”, array2);
9. }
11. #pragma mark 数组排序2
12. void arraySort2() {
13. Student *stu1 = [Student studentWithFirstname:@”MingJie” lastname:@”Li”];
14. Student *stu2 = [Student studentWithFirstname:@”LongHu” lastname:@”Huang”];
15. Student *stu3 = [Student studentWithFirstname:@”LianJie” lastname:@”Li”];
16. Student *stu4 = [Student studentWithFirstname:@”Jian” lastname:@”Xiao”];
17. NSArray *array = [NSArray arrayWithObjects:stu1,stu2,stu3, stu4, nil nil];
18. // 指定排序的比较方法
19. NSArray *array2 = [array sortedArrayUsingSelector:@selector(compareStudent:)];
20. NSLog(@”array2:%@”, array2);
21. }
22. • (NSComparisonResult)compareStudent:(Student *)stu {
23. // 先按照姓排序
24. NSComparisonResult result = [self.lastname compare:stu.lastname];
25. // 如果有相同的姓，就比较名字
26. if (result == NSOrderedSame) {
27. result = [self.firstname compare:stu.firstname];
28. }
29. return result;
30. }
32. #pragma mark 数组排序3
33. void arraySort3() {
34. Student *stu1 = [Student studentWithFirstname:@”MingJie” lastname:@”Li”];
35. Student *stu2 = [Student studentWithFirstname:@”LongHu” lastname:@”Huang”];
36. Student *stu3 = [Student studentWithFirstname:@”LianJie” lastname:@”Li”];
37. Student *stu4 = [Student studentWithFirstname:@”Jian” lastname:@”Xiao”];
38. NSArray *array = [NSArray arrayWithObjects:stu1,stu2,stu3, stu4, nil nil];
40. // 利用block进行排序
41. NSArray *array2 = [array sortedArrayUsingComparator:
42. ^NSComparisonResult(Student obj1, Student obj2) {
43. // 先按照姓排序
44. NSComparisonResult result = [obj1.lastname compare:obj2.lastname];
45. // 如果有相同的姓，就比较名字
46. if (result == NSOrderedSame) {
47. result = [obj1.firstname compare:obj2.firstname];
48. }
50. return result;
51. }];
53. NSLog(@”array2:%@”, array2);
54. }
56. #pragma mark 数组排序4-高级排序
57. void arraySort4() {
58. Student *stu1 = [Student studentWithFirstname:@”MingJie” lastname:@”Li” bookName:@”book1”];
59. Student *stu2 = [Student studentWithFirstname:@”LongHu” lastname:@”Huang” bookName:@”book2”];
60. Student *stu3 = [Student studentWithFirstname:@”LianJie” lastname:@”Li” bookName:@”book2”];
61. Student *stu4 = [Student studentWithFirstname:@”Jian” lastname:@”Xiao” bookName:@”book1”];
62. NSArray *array = [NSArray arrayWithObjects:stu1,stu2,stu3, stu4, nil nil];
64. // 1.先按照书名进行排序
65. // 这里的key写的是@property的名称
66. NSSortDescriptor *bookNameDesc = [NSSortDescriptor sortDescriptorWithKey:@”book.name” ascending:YES];
67. // 2.再按照姓进行排序
68. NSSortDescriptor *lastnameDesc = [NSSortDescriptor sortDescriptorWithKey:@”lastname” ascending:YES];
69. // 3.再按照名进行排序
70. NSSortDescriptor *firstnameDesc = [NSSortDescriptor sortDescriptorWithKey:@”firstname” ascending:YES];
71. // 按顺序添加排序描述器
72. NSArray *descs = [NSArray arrayWithObjects:bookNameDesc, lastnameDesc, firstnameDesc, nil nil];
74. NSArray *array2 = [array sortedArrayUsingDescriptors:descs];
76. NSLog(@”array2:%@”, array2);
77. }