Objective-C：Foundation框架-常用类-NSArray

　　NSArray是用来存储对象的有序列表（NSSet是没有顺序的），它是不可变的。NSArray不能存储C语言中的基本数据类型，如int\float\enum\struct等，也不能存储nil。其用法如下：

 #pragma mark 创建一个数组
 void arrayCreate() {
     // 创建一个空的数组
     NSArray *array = [NSArray array];

     // 创建有1个元素的数组
     array = [NSArray arrayWithObject:@""];

     // 创建有多个元素的数组
     array = [NSArray arrayWithObjects:@"a", @"b", @"c", nil];

     int count = [array count];
     // count = array.count;
     NSLog(@"%i", count);
 }

 #pragma mark 数组的简单使用
 void arrayUse() {
     NSObject *obj = [[NSObject alloc] init];
     NSArray *array = [NSArray arrayWithObjects:@"a", @"b", @"c" , obj, nil];
     // 判断是否包含了某个元素
     if ([array containsObject:@"a"]) {
         NSLog(@"包含了字符串a");
     }

     NSString *last = [array lastObject];
     NSLog(@"last=%@", last);

     NSString *str = [array objectAtIndex:];
     NSLog(@"%@", str);

     int index = [array indexOfObject:@"c"];
     NSLog(@"index=%i", index);

     [obj release];
 }

 #pragma mark 数组的内存管理
 void arrayMemory() {
     //
     Student *stu1 = [[Student alloc] init];
     Student *stu2 = [[Student alloc] init];
     Student *stu3 = [[Student alloc] init];

     NSLog(@"stu1:%zi", [stu1 retainCount]);

     // 当把一个对象塞进数组中时，这个对象的计数器会加1，也就是说数组会对它做一次retain操作
     //
     NSArray *array = [[NSArray alloc] initWithObjects:stu1, stu2, stu3, nil];

     NSLog(@"stu1:%zi", [stu1 retainCount]);

     NSLog(@"count=%zi", array.count);

     //
     [stu1 release];
     [stu2 release];
     [stu3 release];

     // 数组被销毁的时候，会对内部的所有元素都做一次release操作
     //
     [array release];
 }

 #pragma mark 给数组里面的元素发送消息
 void arrayMessage() {
     Student *stu1 = [Student student];
     Student *stu2 = [Student student];
     Student *stu3 = [Student student];

     NSArray *array = [NSArray arrayWithObjects:stu1, stu2, stu3, nil];
     // 让数组里面的所有对象都调用test方法
     // [array makeObjectsPerformSelector:@selector(test)];
     [array makeObjectsPerformSelector:@selector(test2:) withObject:@""];
 }

 #pragma mark 遍历数组1
 void arrayFor1() {
     Student *stu1 = [Student student];
     NSArray *array = [NSArray arrayWithObjects:stu1, @"", @"", @"", nil];
     int count = array.count;
     for (int i = ; i<count; i++) {
         // id == void *
         id obj = [array objectAtIndex:i];
         NSLog(@"%i-%@", i, obj);
     }
 }

 #pragma mark 遍历数组2
 void arrayFor2() {
     Student *stu1 = [Student student];
     NSArray *array = [NSArray arrayWithObjects:stu1, @"", @"", @"", nil];
     // 快速遍历
     int i =;
     for (id obj in array) {
         NSLog(@"%i-%@", i, obj);
         i++;
     }
 }

 #pragma mark 遍历数组3
 void arrayFor3() {
     Student *stu1 = [Student student];
     NSArray *array = [NSArray arrayWithObjects:stu1, @"", @"", @"", nil];
     [array enumerateObjectsUsingBlock:
      ^(id obj, NSUInteger idx, BOOL *stop) {
         NSLog(@"%i-%@", idx, obj);

          // 如果索引为1，就停止遍历
          if (idx == ) {
              // 利用指针修改外面BOOL变量的值
              *stop = YES;
          }
     }];
 }

 #pragma mark 遍历数组4
 void arrayFor4() {
     Student *stu1 = [Student student];
     NSArray *array = [NSArray arrayWithObjects:stu1, @"", @"", @"", nil];

     // 获取数组的迭代器
     // NSEnumerator *enumerator = [array objectEnumerator];
     // 反序迭代器（从尾部开始遍历元素）
     NSEnumerator *enumerator = [array reverseObjectEnumerator];

     // allObjects是取出没有被遍历过的对象
     NSArray *array2 = [enumerator allObjects];
     NSLog(@"array2:%@", array2);

     // 获取下一个需要遍历的元素
     id obj = nil;
     while (obj = [enumerator nextObject]) {
         NSLog(@"obj=%@", obj);
     }
 }

#import <Foundation/Foundation.h>

@interface Book : NSObject
@property (nonatomic, retain) NSString *name;

+ (id)bookWithName:(NSString *)name;
@end

#import "Book.h"

@implementation Book

+ (id)bookWithName:(NSString *)name {
    Book *book = [[[Book alloc] init] autorelease];
    book.name = name;
    return book;
}

- (void)dealloc {
    [_name release];
    [super dealloc];
}
@end

 #pragma mark 派生出新的数组
 void arrayNew() {
     NSArray *array = [NSArray arrayWithObjects:@"", @"", nil];

     NSArray *array2 = [array arrayByAddingObject:@""];

     NSArray *array3 = [array arrayByAddingObjectsFromArray:[NSArray arrayWithObjects:@"", @"", nil]];

     NSLog(@"array:%@", array);
     NSLog(@"array2:%@", array2);
     NSLog(@"array3:%@", array3);

     NSArray *array4 = [NSArray arrayWithObjects:@"", @"", @"", @"", nil];
     NSRange range = NSMakeRange(, );
     NSArray *array5 = [array4 subarrayWithRange:range];
     NSLog(@"array5:%@", array5);
 }

 #pragma mark 数组的其他用法
 void arrayOther() {
     NSArray *array = [NSArray arrayWithObjects:@"", @"", @"", @"", nil];
     // 1-2-3-4
     // 利用分隔符-拼接所有的数组元素
     NSString *str = [array componentsJoinedByString:@"-"];
     NSLog(@"%@", str);

     // 将一个数组写入文件（生成的是一个xml文件）
     NSString *path = @"/Users/apple/Desktop/array.xml";
     [array writeToFile:path atomically:YES];

     path = @"/Users/apple/Desktop/array.txt";
     // 从文件中读取数组内容（文件有严格的格式要求）
     NSArray *array2 = [NSArray arrayWithContentsOfFile:path];
     NSLog(@"array2:%@", array2);
 }

 #pragma mark 数组排序1
 void arraySort1() {
     NSArray *array = [NSArray arrayWithObjects:@"", @"", @"", @"", nil];

     // 返回一个排好序的数组，原来数组的元素顺序不会改变
     // 指定元素的比较方法：compare:
     NSArray *array2 = [array sortedArrayUsingSelector:@selector(compare:)];
     NSLog(@"array2:%@", array2);
 }

 #pragma mark 数组排序2
 void arraySort2() {
     Student *stu1 = [Student studentWithFirstname:@"MingJie" lastname:@"Li"];
     Student *stu2 = [Student studentWithFirstname:@"LongHu" lastname:@"Huang"];
     Student *stu3 = [Student studentWithFirstname:@"LianJie" lastname:@"Li"];
     Student *stu4 = [Student studentWithFirstname:@"Jian" lastname:@"Xiao"];
     NSArray *array = [NSArray arrayWithObjects:stu1,stu2,stu3, stu4, nil];

     // 指定排序的比较方法
     NSArray *array2 = [array sortedArrayUsingSelector:@selector(compareStudent:)];

     NSLog(@"array2:%@", array2);
 }

 #pragma mark 数组排序3
 void arraySort3() {
     Student *stu1 = [Student studentWithFirstname:@"MingJie" lastname:@"Li"];
     Student *stu2 = [Student studentWithFirstname:@"LongHu" lastname:@"Huang"];
     Student *stu3 = [Student studentWithFirstname:@"LianJie" lastname:@"Li"];
     Student *stu4 = [Student studentWithFirstname:@"Jian" lastname:@"Xiao"];
     NSArray *array = [NSArray arrayWithObjects:stu1,stu2,stu3, stu4, nil];

     // 利用block进行排序
     NSArray *array2 = [array sortedArrayUsingComparator:
      ^NSComparisonResult(Student *obj1, Student *obj2) {
          // 先按照姓排序
          NSComparisonResult result = [obj1.lastname compare:obj2.lastname];
          // 如果有相同的姓，就比较名字
          if (result == NSOrderedSame) {
              result = [obj1.firstname compare:obj2.firstname];
          }

          return result;
     }];

     NSLog(@"array2:%@", array2);
 }

 #pragma mark 数组排序4-高级排序
 void arraySort4() {
     Student *stu1 = [Student studentWithFirstname:@"MingJie" lastname:@"Li" bookName:@"book1"];
     Student *stu2 = [Student studentWithFirstname:@"LongHu" lastname:@"Huang" bookName:@"book2"];
     Student *stu3 = [Student studentWithFirstname:@"LianJie" lastname:@"Li" bookName:@"book2"];
     Student *stu4 = [Student studentWithFirstname:@"Jian" lastname:@"Xiao" bookName:@"book1"];
     NSArray *array = [NSArray arrayWithObjects:stu1,stu2,stu3, stu4, nil];

     // 1.先按照书名进行排序
     // 这里的key写的是@property的名称
     NSSortDescriptor *bookNameDesc = [NSSortDescriptor sortDescriptorWithKey:@"book.name" ascending:YES];
     // 2.再按照姓进行排序
     NSSortDescriptor *lastnameDesc = [NSSortDescriptor sortDescriptorWithKey:@"lastname" ascending:YES];
     // 3.再按照名进行排序
     NSSortDescriptor *firstnameDesc = [NSSortDescriptor sortDescriptorWithKey:@"firstname" ascending:YES];
     // 按顺序添加排序描述器
     NSArray *descs = [NSArray arrayWithObjects:bookNameDesc, lastnameDesc, firstnameDesc, nil];

     NSArray *array2 = [array sortedArrayUsingDescriptors:descs];

     NSLog(@"array2:%@", array2);
 }