Question

在没有foreach循环的情况下，是否有更简洁的方法来实现代码重用？

IEnumerable<Stream> GetStreams() {
    // nope
    // yield return GetStreamsHelper(); 

    // nope
    // return GetStreamsHelper(); 

    // yup
    foreach (var x in GetStreamsHelper()) {
        yield return x;
    }
}

IEnumerable<Stream> GetStreamsHelper() {
   using (var stream = OpenStream()) {
        yield return stream;
   }
}

这是我尝试实现的更完整的例子：

    class MoreCompleteExample {
        IEnumerable<Stream> GetStreams() {
            string[] files = new[] { "f1", "f2" };
            foreach (var f in files) {
                // HERE I WANT TO USE A HELPER METHOD
                // NOTHING SEEMS TO WORK EXCEPT A foreach
                // PERHAPS THERE IS A LINQ-y WAY TO WRITE THE foreach?
                //return GetStreamsHelper(f);                    
                //yield return GetStreamsHelper(f);                    
                foreach (var x in GetStreamsHelper(f)) {
                    yield return x;
                }

            }
        }

        IEnumerable<Stream> GetStreamsHelper(string filename) {
            using (var stream = new FileStream(filename, FileMode.Open)) {
                Diddle(stream);
                yield return stream;
                Caress(stream);
            }
        }
        void Diddle(Stream stream) { /* show the stream some love */ }
        void Caress(Stream stream) { /* that was nice but i gotsa go */ }

    }

Answer 1

您必须枚举您的收藏品才能使用收益率。如果您不想在方法中迭代集合，可以将代码更改为下一个代码：

IEnumerable<Stream> GetStreams() {
    return GetStreamsHelper(); 
}

然后你将遍历你方法的集合。

C＃嵌套产量 - 实现代码重用的最简洁方法？

1 个答案: