数组的排序与遍历

1.创建数组

　　// 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 nil];
NSArray *array3 = [array arrayByAddingObjectsFromArray:[NSArray arrayWithObjects:@"4", @"5", nil nil]];

NSArray *array4 = [NSArray arrayWithObjects:@"1", @"2", @"3", @"4", nil nil];
NSRange range = NSMakeRange(1, 2);
NSArray *array5 = [array4 subarrayWithRange:range];

2.数组的一些基本方法

int count = [array count];//个数
// 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];最后一个元素
NSString *str = [array objectAtIndex:1];根据索引获取数组中的元素
int index = [array indexOfObject:@"c"];获取指定元素的索引
// 让数组里面的所有对象都调用test方法，123为参数
NSArray *array = [NSArray arrayWithObjects:stu1, stu2, stu3, nil nil];
[array makeObjectsPerformSelector:@selector(test2:) withObject:@"123"];
NSArray *array = [NSArray arrayWithObjects:@"1", @"2", @"3", @"4", nil nil];
// 1-2-3-4
// 利用分隔符-拼接所有的数组元素
NSString *str = [array componentsJoinedByString:@"-"];
// 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];

3.遍历数组

 

#pragma mark 遍历数组1
void arrayFor1() {
    NSArray *array = [NSArray arrayWithObjects:stu1, @"1", @"2", @"3", nil nil];
    int count = array.count;
    for (int i = 0; i<count; i++) {
        id obj = [array objectAtIndex:i];
    }
}

#pragma mark 遍历数组2 快速遍历
void arrayFor2() {
    Student *stu1 = [Student student];
    NSArray *array = [NSArray arrayWithObjects:stu1, @"1", @"2", @"3", nil nil];
    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 nil];
    [array enumerateObjectsUsingBlock:
     ^(id obj, NSUInteger idx, BOOLBOOL *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 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);
    }
}

4.数组排序

 

 

#pragma mark 数组排序1
void arraySort1() {
    NSArray *array = [NSArray arrayWithObjects:@"2", @"3", @"1", @"4", nil 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 nil];
    // 指定排序的比较方法
    NSArray *array2 = [array sortedArrayUsingSelector:@selector(compareStudent:)];
    NSLog(@"array2:%@", array2);
}
- (NSComparisonResult)compareStudent:(Student *)stu {
    // 先按照姓排序
    NSComparisonResult result = [self.lastname compare:stu.lastname];
    // 如果有相同的姓，就比较名字
    if (result == NSOrderedSame) {
        result = [self.firstname compare:stu.firstname];
    }
    return result;
}

#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 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 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 nil];

    NSArray *array2 = [array sortedArrayUsingDescriptors:descs];

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