CODEWITHSUNDEEP
julia
TylerD
TylerD

Reputation: 469

Add element to NamedTuple

I have written a function that adds an element to a NamedTuple:

function Base.setindex!(nt::NamedTuple, key::String, value::Any)
    return (; nt..., key=value)
end

nt = (; a=1, b=2)
setindex!(nt, "c", 3)

The issue is though that the added value has the key "key", and not the actual string that key represents as seen below:

(a = 1, b = 2, key = 3)

How can I "evaluate" the key-variable before adding it to the NamedTuple?

Upvotes: 3

Views: 401

Answers (2)

Przemyslaw Szufel
Przemyslaw Szufel

Reputation: 42214

You could also try using Accessors. This is a Julia package providing a macro based syntax for working with immutable types. This syntax makes the code more readable.

julia> using Accessors

julia> nt = (;a=1, b=2)
(a = 1, b = 2)

julia> new_nt = @set nt.a = 33
(a = 33, b = 2)

julia> new_nt = @insert new_nt.c = 44
(a = 33, b = 2, c = 44)

Upvotes: 1

Bogumił Kamiński
Bogumił Kamiński

Reputation: 69879

This is how I would do it (note that this creates a new NamedTuple and does not update the passed nt as this is not possible):

julia> setindex(nt::NamedTuple, key::AbstractString, value) =
           merge(nt, (Symbol(key) => value,))
setindex (generic function with 2 methods)

julia> setindex((a=1, b=2), "c", 3)
(a = 1, b = 2, c = 3)

julia> setindex((a=1, b=2), "b", 3) # note what happens if you re-use the key that is already present
(a = 1, b = 3)

Upvotes: 3

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