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intfloatenumstruct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:@"123"];
    
    // 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:1];
    NSLog(@"%@", str);
    
    int index = [array indexOfObject:@"c"];
    NSLog(@"index=%i", index);
    
    [obj release];
}

#pragma mark 数组的内存管理
void arrayMemory() {
    // 1
    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
    // 2
    NSArray *array = [[NSArray alloc] initWithObjects:stu1, stu2, stu3, nil];
    
    NSLog(@"stu1:%zi", [stu1 retainCount]);
    
    NSLog(@"count=%zi", array.count);
    
    // 1
    [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
    // 0
    [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:@"123"];
}

#pragma mark 遍历数组1
void arrayFor1() {
    Student *stu1 = [Student student];
    NSArray *array = [NSArray arrayWithObjects:stu1, @"1", @"2", @"3", nil];
    int count = array.count;
    for (int i = 0; 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, @"1", @"2", @"3", nil];
    // 快速遍历
    int i =0;
    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, @"1", @"2", @"3", 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 == 1) {
             // 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, @"1", @"2", @"3", 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:@"1", @"2", nil];
    
    NSArray *array2 = [array arrayByAddingObject:@"3"];
    
    NSArray *array3 = [array arrayByAddingObjectsFromArray:[NSArray arrayWithObjects:@"4", @"5", nil]];
    
    NSLog(@"array:%@", array);
    NSLog(@"array2:%@", array2);
    NSLog(@"array3:%@", array3);
    
    
    NSArray *array4 = [NSArray arrayWithObjects:@"1", @"2", @"3", @"4", nil];
    NSRange range = NSMakeRange(1, 2);
    NSArray *array5 = [array4 subarrayWithRange:range];
    NSLog(@"array5:%@", array5);
}

#pragma mark 数组的其他用法
void arrayOther() {
    NSArray *array = [NSArray arrayWithObjects:@"1", @"2", @"3", @"4", 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:@"2", @"3", @"1", @"4", 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);
}