lesson_06_block

最新推荐文章于 2023-05-08 22:10:01 发布

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本文通过几个实战案例介绍Objective-C中Block的使用方法，包括字符串比较、数组元素查找及数组排序等功能。通过这些示例，读者可以了解如何定义Block并应用于实际编程任务。

        //定义一个block，返回值是BOOL,有两个NSString参数，实现：判断字符串是否相等；
//        NSString *str1 = @"js";
//        NSString *str2 = @"jsrrr";
//        BOOL (^block) (NSString *, NSString *) = ^(NSString* str1,NSString * str2){
//            return [str1 isEqualToString:str2];
//        };
//        NSLog(@"%hhd",block(str1,str2));




//        NSComparisonResult (^sortBlock)(id, id) = ^(id obj1, id obj2){
//            //默认升序
//            NSString *str1 = obj1;
//            NSString *str2 = obj2;
//            return [str1 compare: str2];
//        };
//        NSLog(@"%ld", sortBlock(str1,str2));






        //定义一个block，返回值为NSInteger,有两个参数，一个是NSArray,一个是NSString.实现：判断数组是否包含此字符串，如果包含，返回字符串的下标，如果不包含，返回-1.
        NSArray *arr1 = [NSArray arrayWithObjects:@"laoda",@"laoer",@"laosan", @"laosi",nil];

        NSString *str3 = [NSString stringWithFormat:@"laosn"];

        //方式一：
        BOOL (^block)(NSArray *, NSString *) = ^ BOOL (NSArray *arr1, NSString *str3){
            for (int i = 0; i < [arr1 count]; i ++) {
                if ([arr1[i] isEqualToString:str3]) {
                    return i;
                }
            }
            return -1;
        };
        NSLog(@"%hhd", block(arr1, str3));

        //方式二：

        int (^block1) (NSArray *, NSString *) = ^(NSArray *array, NSString * string){
            if ([array containsObject:string]) {
                return (int) [array indexOfObject:string];
            }
            return -1;
        };
        NSLog(@"%d", block1(arr1, @"ss"));
        NSLog(@"%d", block(arr1,str3));


        //创建一个数组，初始化为@"123", @"21" ,@"33", @"69", @"108", @"256",使用block语法进行数组的排序，并输出内容，
        //排序结果，：108 123 21 256 33 69

        //提示：sortedArrayWithOptions:usingComparator;

/*        NSArray *arr2 = [NSArray arrayWithObjects:@"123", @"21" ,@"33", @"69", @"108", @"256", nil];


        arr2 = [arr2 sortedArrayUsingComparator:^NSComparisonResult(id obj1, id obj2) {
            NSString *s1 = obj1;
            NSString *s2 = obj2;
            if ([s1 compare:s2] == 1) {
                return NSOrderedDescending;
            }
            else if ([s1 compare:s2] == -1){
                return NSOrderedAscending;
            }else {
                return NSOrderedSame;
            }
        }];

        NSLog(@"%@" ,arr2);
*/
/*
        NSArray *arr3 = @[@"123", @"21" ,@"33", @"69", @"108", @"256"];
        arr3 = [arr3 sortedArrayUsingComparator:^NSComparisonResult(id obj1, id obj2) {
            NSString *str3 = obj1;
            NSString *str4 = obj2;
            if ([str3 isEqualToString:str4] == 1) {
                return NSOrderedDescending;
            } else if([str3 isEqualToString:str4] == -1 ){
                return NSOrderedAscending;
            }else{
                return NSOrderedSame;
            }

        }];
*/
        NSArray *arr4 = @[@123,@21 ,@33,@69,@108,@256];
        arr4 = [arr4 sortedArrayUsingComparator:^NSComparisonResult(id obj1, id obj2) {
            if (obj1 < obj2){
                return NSOrderedAscending;
            }else if (obj1 > obj2){
                return NSOrderedDescending;
            }else{
                return NSOrderedSame;
            };

        }];

        NSLog(@"%@", arr4);


/*        arr4 = [arr4 sortedArrayUsingComparator:^NSComparisonResult(id obj1, id obj2) {
            NSString *str1 = obj1;
            NSString *str2 = obj2;
            if ([str1 isEqualToString:str2] == 1) {
                return NSOrderedDescending;
            }else if ([str1 isEqualToString:str2] == -1){
                return NSOrderedAscending;
            }else{
                return NSOrderedSame;
            }
        }];
*/




        //预习categroy .extension he Protocol;