1.创建数组

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// 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

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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

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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
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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);  

}