如何使用curl客户端证书身份验证上传？(How to upload with curl client certificate authentication?)

 通常会将def版本编写为： 
 
def f2(a:Int) = a+1
 
 如果你按照自己的方式编写它，它实际上是在创建一个方法f2 ，当被调用时，构造一个新的函数闭包。 所以在你的两种情况下，你仍然有一个功能。 但在第一种情况下，函数只构造一次并存储（如f1 ）供以后使用。 但在第二种情况下，每次引用f2都会构造函数，这是一种浪费。 
 
 那么什么时候比一个方法更喜欢一个函数呢？ 那么，在某些情况下，您可以更轻松地使用函数。 考虑这种情况： 
 
(1 to 3).map(f1 andThen f1)    // totally fine
(1 to 3).map(f2 andThen f1)    // "missing arguments" error
(1 to 3).map(f2 _ andThen f1)  // fixed by adding "_" after the method name
 
 因此f1始终是一个函数，因此您可以调用类似于andThen的方法。 变量f2代表一种方法，所以它不希望像这样使用; 它总是希望跟随论证。 您可以随后通过下划线将方法转换为函数，但如果没有必要，这可能看起来有点难看。 

Typically one would write the def version as:
 
def f2(a:Int) = a+1
 
If you write it they way you did, it's actually creating a method f2 that, when called, constructs a new function closure. So in both of your cases, you still have a function. But in the first case, the function gets constructed only once and stored (as f1) for later use. But in the second case, the function gets constructed every time f2 is referenced, which is kind of a waste.
 
So when to prefer a function over a method? Well, you can work with a function a bit more easily in certain situations. Consider this case:
 
(1 to 3).map(f1 andThen f1)    // totally fine
(1 to 3).map(f2 andThen f1)    // "missing arguments" error
(1 to 3).map(f2 _ andThen f1)  // fixed by adding "_" after the method name
 
So f1 is always a function and so you can call a method like andThen on it. The variable f2 represents a method, so it doesn't expect to be used like this; it always expects to be followed by arguments. You can always turn a method into a function by following it with an underscore, but this can look a little ugly if it's not necessary.