问题
How to pass a tuple argument the best way ?
Example:
def foo(...): (Int, Int) = ...
def bar(a: Int, b: Int) = ...
Now I would like to pass the output of foo to bar. This can be achieved with:
val fooResult = foo(...)
bar(fooResult._1, fooResult._2)
This approach looks a bit ugly, especially when we deal with a n-tuple with n > 2. Also we have to store the result of foo in an extra value, because otherwise foo has to be executed more than once using bar(foo._1, foo._2).
Is there a better way to pass through the tuple as argument ?
回答1:
There is a special tupled method available for every function:
val bar2 = (bar _).tupled // or Function.tupled(bar _)
bar2 takes a tuple of (Int, Int) (same as bar arguments). Now you can say:
bar2(foo())
If your methods were actually functions (notice the val keyword) the syntax is much more pleasant:
val bar = (a: Int, b: Int) => //...
bar.tupled(foo())
See also
- How to apply a function to a tuple?
回答2:
Using tupled, as @Tomasz mentions, is a good approach.
You could also extract the tuple returned from foo during assignment:
val (x, y) = foo(5)
bar(x, y)
This has the benefit of cleaner code (no _1 and _2), and lets you assign descriptive names for x and y, making your code easier to read.
回答3:
It is worth also knowing about
foo(...) match { case (a,b) => bar(a,b) }
as an alternative that doesn't require you to explicitly create a temporary fooResult. It's a good compromise when speed and lack of clutter are both important. You can create a function with bar _ and then convert it to take a single tuple argument with .tupled, but this creates a two new function objects each time you call the pair; you could store the result, but that could clutter your code unnecessarily.
For everyday use (i.e. this is not the performance-limiting part of your code), you can just
(bar _).tupled(foo(...))
in line. Sure, you create two extra function objects, but you most likely just created the tuple also, so you don't care that much, right?
来源：https://stackoverflow.com/questions/12230698/how-to-pass-a-tuple-argument-the-best-way