thojanssens1
Dynamic operator in argument of macro function?
I have an operator in a variable, for example:
guard = &Kernel.>=/2
How can I use that variable as argument to a macro, e.g. for Ecto.Query.where/3?
Ecto.Query.where(query, [..., r], field(r, ^field) >= ^value)
I want to replace the operator hard-coded above by the one dynamically defined in the variable guard.
Marked As Solved
ityonemo
Looking at the code it seems like that’s not something you can do. A macro transforms AST at compile time, and you’re trying to gate it on something that exists only at runtime.
Also Liked
NobbZ
How exactly you have to use variables in a macro depends on the Macro. You already see it in ecto where the names are used to build the query, except when you pin (^), then you use the variables value in the query.
Though, passing in the operator like that is not possible. I think you’ll have to limit yourt choices to a handfull of operators and branch on them, eg:
case op do
:">=" -> Ecto.Query.where(query, [..., r], field(r, ^field) >= ^value)
:"<" -> Ecto.Query.where(query, [..., r], field(r, ^field) < ^value)
end
Popular in Questions
Other popular topics
Latest on Elixir Forum
Sponsor Spotlight
Develop your skills with books, videos, and courses.
Categories:
Sub Categories:
Forums
Our Sponsors
Build Elixir applications with speed and confidence.
Supporting innovation across the BEAM ecosystem.
We build reliable cloud platforms for business-critical systems.
Catch errors, track performance, monitor hosts and more.
Producing high quality Elixir screencasts since 2017.
Enabling companies to succeed by building software people love.
The deployment platform built for Elixir: PaaS ease, VPS control.
Courses that'll move you from confusion to "Aha, now I get it!"