Pass function argument as code block

Question

I am new to Scala. I have been searching but there is no easy "search string" for the seemingly easy question I have.

def foo( f: (String) => String ){println(f("123"))}
foo{_+"abc"} //works

def bar( f :() => String ){println(f())}
bar{"xyz"} // why does this not work?

def baz( f: => String ){println(f)}
baz{"xyz"} //works

Why does the second (bar) not work?

Answer 1

Second baz works because it's not a function literal, but a call-by-name parameter. Basically what it does is delaying the moment of argument computation until it's needed in the program. You can also read about this in this question. As for bar you just need to pass a function like bar{() => "xyz"}

Answer 2

bar accepts a function that takes no arguments and returns String. You gave it just a String. To make it work:

bar{() => "xyz"}