Converting String to Symbol during struct construction

[sstroemer]

@goerch

Adding a second constructor

MyStruct(id::Int, value::String, kwargs...) = MyStruct(id=id, value=Symbol(value), kwargs...)

makes this work for me.

This seems to only work due to essentially eliminating kwargs... in the MWE. Consider the following change, that breaks it again:

Base.@kwdef mutable struct MyStruct
    id::Int
    value::Symbol = :fixed
    notimportant::Int = -1
end
MyStruct(id::Int, value::String, kwargs...) = MyStruct(id=id, value=Symbol(value), kwargs...)

MyStruct(id=1, value="a")     # this fails again

---

@Bardo

You could put the conversion into the constructor:

Base.@kwdef mutable struct MyStruct
    id::Int
    value::Symbol = :fixed
end
MyStruct(value::Symbol, kwargs...) = MyStruct(value, kwargs...)

MyStruct(id=2, value=Symbol(:a))
MyStruct(id=2, value=Symbol("b"))

While this certainly works, it achieves something else and does not solve the initial problem. It converts the String to a Symbol ahead of construction of the struct, instead of during. While this seems like a valid fix, consider the following:

• I have a large “data storage” (the struct), that is initialized using data parsed from a file (yaml, csv, …). I read in Strings. This is fairly efficient for most fields. Later on I come to a point where profiling shows that keeping a specific field as Symbol makes sense (due the timeloss of doing Symbol("somestring") after reading the data, using Symbols can be worse than Strings for many fields).
• I construct this struct at several points of my code. If I need to “symbolify” a new field, I need to change this everywhere instead of at a single central point (the constructor).