关于数组的知识
2015-09-23 07:59 真实16 阅读(325) 评论(0) 编辑 收藏 举报[objc] view plaincopy
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// 创建一个空的数组
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NSArray *array = [NSArray array];
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// 创建有1个元素的数组
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array = [NSArray arrayWithObject:@"123"];
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// 创建有多个元素的数组
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array = [NSArray arrayWithObjects:@"a", @"b", @"c", nil nil];
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NSArray *array3 = [array arrayByAddingObjectsFromArray:[NSArray arrayWithObjects:@"4", @"5", nil nil]];
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NSArray *array4 = [NSArray arrayWithObjects:@"1", @"2", @"3", @"4", nil nil];
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NSRange range = NSMakeRange(1, 2);
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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
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// 判断是否包含了某个元素
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if ([array containsObject:@"a"]) {
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NSLog(@"包含了字符串a");
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}
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NSString *last = [array lastObject];最后一个元素
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NSString *str = [array objectAtIndex:1];根据索引获取数组中的元素
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int index = [array indexOfObject:@"c"];获取指定元素的索引
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// 让数组里面的所有对象都调用test方法，123为参数
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NSArray *array = [NSArray arrayWithObjects:stu1, stu2, stu3, nil nil];
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[array makeObjectsPerformSelector:@selector(test2:) withObject:@"123"];
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NSArray *array = [NSArray arrayWithObjects:@"1", @"2", @"3", @"4", nil nil];
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// 1-2-3-4
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// 利用分隔符-拼接所有的数组元素
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NSString *str = [array componentsJoinedByString:@"-"];
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// 将一个数组写入文件（生成的是一个xml文件）
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NSString *path = @"/Users/apple/Desktop/array.xml";
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[array writeToFile:path atomically:YES];
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path = @"/Users/apple/Desktop/array.txt";
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// 从文件中读取数组内容（文件有严格的格式要求）
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NSArray *array2 = [NSArray arrayWithContentsOfFile:path];
3.遍历数组
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#pragma mark 遍历数组1
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void arrayFor1() {
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NSArray *array = [NSArray arrayWithObjects:stu1, @"1", @"2", @"3", nil nil];
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int count = array.count;
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for (int i = 0; i<count; i++) {
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id obj = [array objectAtIndex:i];
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}
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}
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#pragma mark 遍历数组2 快速遍历
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void arrayFor2() {
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Student *stu1 = [Student student];
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NSArray *array = [NSArray arrayWithObjects:stu1, @"1", @"2", @"3", nil nil];
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int i =0;
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for (id obj in array) {
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NSLog(@"%i-%@", i, obj);
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i++;
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}
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}
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#pragma mark 遍历数组3
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void arrayFor3() {
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Student *stu1 = [Student student];
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NSArray *array = [NSArray arrayWithObjects:stu1, @"1", @"2", @"3", nil nil];
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[array enumerateObjectsUsingBlock:
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^(id obj, NSUInteger idx, BOOLBOOL *stop) {
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NSLog(@"%i-%@", idx, obj);
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// 如果索引为1，就停止遍历
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if (idx == 1) {
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// 利用指针修改外面BOOL变量的值
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*stop = YES;
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}
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}];
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}
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#pragma mark 遍历数组4
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void arrayFor4() {
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Student *stu1 = [Student student];
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NSArray *array = [NSArray arrayWithObjects:stu1, @"1", @"2", @"3", nil nil];
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// 获取数组的迭代器
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// NSEnumerator *enumerator = [array objectEnumerator];
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// 反序迭代器（从尾部开始遍历元素）
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NSEnumerator *enumerator = [array reverseObjectEnumerator];
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// allObjects是取出没有被遍历过的对象
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NSArray *array2 = [enumerator allObjects];
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NSLog(@"array2:%@", array2);
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// 获取下一个需要遍历的元素
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id obj = nil;
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while (obj = [enumerator nextObject]) {
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NSLog(@"obj=%@", obj);
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}
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}
4.数组排序
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#pragma mark 数组排序1
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void arraySort1() {
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NSArray *array = [NSArray arrayWithObjects:@"2", @"3", @"1", @"4", nil nil];
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// 返回一个排好序的数组，原来数组的元素顺序不会改变
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// 指定元素的比较方法：compare:
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NSArray *array2 = [array sortedArrayUsingSelector:@selector(compare:)];
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NSLog(@"array2:%@", array2);
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}
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#pragma mark 数组排序2
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void arraySort2() {
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Student *stu1 = [Student studentWithFirstname:@"MingJie" lastname:@"Li"];
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Student *stu2 = [Student studentWithFirstname:@"LongHu" lastname:@"Huang"];
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Student *stu3 = [Student studentWithFirstname:@"LianJie" lastname:@"Li"];
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Student *stu4 = [Student studentWithFirstname:@"Jian" lastname:@"Xiao"];
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NSArray *array = [NSArray arrayWithObjects:stu1,stu2,stu3, stu4, nil nil];
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// 指定排序的比较方法
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NSArray *array2 = [array sortedArrayUsingSelector:@selector(compareStudent:)];
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NSLog(@"array2:%@", array2);
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}
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- (NSComparisonResult)compareStudent:(Student *)stu {
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// 先按照姓排序
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NSComparisonResult result = [self.lastname compare:stu.lastname];
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// 如果有相同的姓，就比较名字
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if (result == NSOrderedSame) {
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result = [self.firstname compare:stu.firstname];
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}
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return result;
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}
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#pragma mark 数组排序3
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void arraySort3() {
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Student *stu1 = [Student studentWithFirstname:@"MingJie" lastname:@"Li"];
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Student *stu2 = [Student studentWithFirstname:@"LongHu" lastname:@"Huang"];
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Student *stu3 = [Student studentWithFirstname:@"LianJie" lastname:@"Li"];
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Student *stu4 = [Student studentWithFirstname:@"Jian" lastname:@"Xiao"];
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NSArray *array = [NSArray arrayWithObjects:stu1,stu2,stu3, stu4, nil nil];
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// 利用block进行排序
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NSArray *array2 = [array sortedArrayUsingComparator:
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^NSComparisonResult(Student *obj1, Student *obj2) {
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// 先按照姓排序
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NSComparisonResult result = [obj1.lastname compare:obj2.lastname];
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// 如果有相同的姓，就比较名字
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if (result == NSOrderedSame) {
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result = [obj1.firstname compare:obj2.firstname];
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}
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return result;
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}];
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NSLog(@"array2:%@", array2);
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}
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#pragma mark 数组排序4-高级排序
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void arraySort4() {
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Student *stu1 = [Student studentWithFirstname:@"MingJie" lastname:@"Li" bookName:@"book1"];
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Student *stu2 = [Student studentWithFirstname:@"LongHu" lastname:@"Huang" bookName:@"book2"];
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Student *stu3 = [Student studentWithFirstname:@"LianJie" lastname:@"Li" bookName:@"book2"];
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Student *stu4 = [Student studentWithFirstname:@"Jian" lastname:@"Xiao" bookName:@"book1"];
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NSArray *array = [NSArray arrayWithObjects:stu1,stu2,stu3, stu4, nil nil];
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// 1.先按照书名进行排序
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// 这里的key写的是@property的名称
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NSSortDescriptor *bookNameDesc = [NSSortDescriptor sortDescriptorWithKey:@"book.name" ascending:YES];
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// 2.再按照姓进行排序
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NSSortDescriptor *lastnameDesc = [NSSortDescriptor sortDescriptorWithKey:@"lastname" ascending:YES];
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// 3.再按照名进行排序
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NSSortDescriptor *firstnameDesc = [NSSortDescriptor sortDescriptorWithKey:@"firstname" ascending:YES];
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// 按顺序添加排序描述器
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NSArray *descs = [NSArray arrayWithObjects:bookNameDesc, lastnameDesc, firstnameDesc, nil nil];
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NSArray *array2 = [array sortedArrayUsingDescriptors:descs];
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NSLog(@"array2:%@", array2);
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}
