# Runtime-calculated default values for structs **URL:** \ **Category:** Proposals: Ideas\ **Tags:** ecto, structs, oban, default\ **Created:** [November 4, 2025, 3:57pm UTC](https://forum.elixirforum.com/t/runtime-calculated-default-values-for-structs/73189 "2025-11-04T15:57:26Z")\ **Posts on this page:** 1\ **Showing post:** 11
**Author:** ![ffloyd](https://forum.elixirforum.com/user_avatar/forum.elixirforum.com/ffloyd/32/10538_2.png) [@ffloyd](https://forum.elixirforum.com/u/ffloyd)\ **Post date:** [November 4, 2025, 6:20pm UTC](https://forum.elixirforum.com/t/runtime-calculated-default-values-for-structs/73189/11 "2025-11-04T18:20:38Z")
Yeah. Let me summarize: 1. Often engineers do `%Struct{}` for creating a new instance of a struct by default. There is no established tradition to create factory functions like in Golang. 2. Elixir allows to set only “static” defaults. So `%Struct{}` already has some implicitness, but at least it is “idempotent” after compilation. 3. For defining a dynamic default each place where `%Struct{}`, `struct(...)`, etc is used should be refactored. - In big codebases it can lead to inadequately expensive refactoring for just introducing a mere dynamic default. - creation of a struct can be inside library code so you may be not able to inject default value at all. 4. Cultural problem: libraries repeat “no dynamic defaults” restriction that does not makes developers life easier, usually opposite. 5. Such limitation is uncommon in other popular languages I can recall. Original proposal solves mentioned problems, but breaks `%Struct{} == %Struct{}` behavior. But without breaking it we cannot make `%Struct{}` respect dynamic defaults. And without this we cannot make adding dynamic defaults cheap in big codebases. ❓ Might be loosing this behavior is acceptable sacrifice? Or we’re missing some smart move here? --- _[View the full topic](https://forum.elixirforum.com/t/runtime-calculated-default-values-for-structs/73189)._