在Zio中输入推断以进行理解
因此，我写了一种方法来计算Zio中文件中的行数。
def lines(file: String): Task[Long] = {
def countLines(reader: BufferedReader): Task[Long] = Task.effect(reader.lines().count())
def releaseReader(reader: BufferedReader): UIO[Unit] = Task.effectTotal(reader.close())
def acquireReader(file: String): Task[BufferedReader] = Task.effect(new BufferedReader(new FileReader(file), 2048))
Task.bracket(acquireReader(file), releaseReader, countLines)
}
现在，当我尝试以这样的方式提取结果时，在我的运行方法中：
for {
lines <- linesV3("src/main/scala/FileIO.scala") //Type of lines showing as Any
_ <- putStrLn(lines.toString) //This line throws error as it cannot convert Any to String
}
线的类型正在出现，而不是长。为什么这样？ 如果我使用flatmap，则可以正确推断该类型。
So I have written a method to count the number of lines in a file in ZIO.
def lines(file: String): Task[Long] = {
def countLines(reader: BufferedReader): Task[Long] = Task.effect(reader.lines().count())
def releaseReader(reader: BufferedReader): UIO[Unit] = Task.effectTotal(reader.close())
def acquireReader(file: String): Task[BufferedReader] = Task.effect(new BufferedReader(new FileReader(file), 2048))
Task.bracket(acquireReader(file), releaseReader, countLines)
}
Now inside my run method when I try to extract the result like this:
for {
lines <- linesV3("src/main/scala/FileIO.scala") //Type of lines showing as Any
_ <- putStrLn(lines.toString) //This line throws error as it cannot convert Any to String
}
The type of lines is coming as Any instead of Long. Why is this so?
If I use flatMap then the type is inferred correctly.
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评论（2）
您在此处发布的代码没有问题。该问题必须来自您计划中的其他地方。
也许您在理解后缺少收益率。我不知道这是否是复制错误。
There's no problem with the code you posted here. The issue must be arising from somewhere else in your program.
Maybe you are missing the yield after the for comprehension. I don't know if that is a copying error.
因此，解决方案相当相似。
在理解后，我一旦添加一个收益率，类型推理就开始正确地工作，
因为PutStrln仅接受字符串参数，因此需要使用Tostring方法。
so the solution was fairly similar.
As soon as I add a yield after the for comprehension the type inference starts working correctly
The toString method is required because putStrLn accepts only String parameters.