On Wednesday, 12 October 2016 at 16:29:22 UTC, Basile B. wrote:
On Tuesday, 11 October 2016 at 20:17:19 UTC, Straivers wrote:
I have a class T with a templated function foo(string
name)(int, int, float) that will be mixed in via template, and
I want to determine if that class has mixed it in such that
foo(name = "bar"). How could I go about this? Thanks.
eg:
mixin template A(string name, Args...) {
void foo(string fooName)(Args args)
if (fooName == name) {}
}
template hasFoo(string name, A) {
enum hasFoo = ???
}
class B {
mixin A!("mash", int, int, string);
}
For this particular example the following solution works:
template A(string name, Args...)
{
void foo(string fooName)(Args args)
if (fooName == name) {}
}
template hasFoo(string name, T, V...)
{
enum hasFoo = __traits(hasMember, T, "foo") &&
is(typeof(T.foo!name) == typeof(A!(name,V).foo!name));
}
class B
{
mixin A!("mash", int, int, string);
}
unittest
{
static assert( hasFoo!("mash", B, int, int , string));
static assert( !hasFoo!("rash", B, int, uint , string));
}
Now I can't say that I's generic enough to validate any members
that's injected.
Note well that it wouldn't work with a regular mixin template.
You can also take a look at "std.traits.TemplateOf"
There is also isTemplate
(https://dlang.org/spec/traits.html#isTemplate). You can check
first that the member exists and then check if it's a template
(though this will pick up more than just template functions).
There's also a *very* ugly hack you can do:
//A template function's .stringof is of the format <function
name>(<template args>)(<function args>)
//so match on the number of brackets to determine whether it's a
template function or not
enum isTemplateFunction = __traits(isTemplate, f)
&& fstr.balancedParens('(', ')')
&& (fstr.canFind("if")
|| fstr.count!(c =>
cast(bool)c.among!('(',
')')) == 4);