I'm trying to do something like the following, and the compiler is not happy...
def foo(db: Database = ctx.defaultDB)(implicit ctx: Context)
That is, if db isn't specified, use ctx to look up the default. The compiler didn't like this version so I tried this:
def foo(ctx: Context, db: Database = ctx.defaultDB)
Compiler didn't like that either...
There are many limitations on default parameter values.
I suggest overloading:
def foo(db: Database)(implicit ctx: Context) = ...
def foo(implicit ctx: Context): Type = foo(ctx.defaultDB)(ctx)
I'm not sure what the exact requirement is, but my quick testing suggests you have to make the return type on the 2nd overload explicit.
This:
def foo(ctx:Context)(db:Database = ctx.defaultDB )
Of course, it isn't implicit. You might be able to make it implicit with a trick like this:
def foo(implicit ctx:Context) = {
class XXX {
def apply(db:Database = ctx.defaultDB) = ...
}
new XXX(ctx)
}
However, that won't work like you expect, because foo(x) will pass x as the implicit, and foo()(x) will give an error. Only foo.apply(x) will work, and that sucks.
How about
def foo(db: Database = implicitly[Context].defaultDB) = ???
