Accessing an element of a structure based off of a string

New to Julia
1

I want to be able to access and change an element of a structure based off a string that has been read in from a text file and then change the value of that element. The element that is being changed could of several different data types. A simplified version of the structure I am working with is shown below:

mutable struct SMALLSTRUCTURE
    POPSIZE::Int64
    POPSIZEMAX::Int64
    SEEDMIN::Int64
    SEEDMAX::Int64
    EXPONENT::Float64
    SIGMAINITIAL::Float64
    SIGMAFINAL::Float64
end


mutable struct BIGSTRUCTURE
    SZEGLOBAL::Int64                       
    NUMVAR::Int64
    MAXITER::Int64
    MINVAL::Float64
    MAXVAL::Float64
    BESTPOINT::Array{Float64,1}
    GLOBALPOP::Array{Float64,2}
    GLOBALCOST::Array{Float64,2}
    IWO::SMALLSTRUCTURE
end
2 
julia> mutable struct SMALLSTRUCTURE
           POPSIZE::Int64
           POPSIZEMAX::Int64
           SEEDMIN::Int64
           SEEDMAX::Int64
           EXPONENT::Float64
           SIGMAINITIAL::Float64
           SIGMAFINAL::Float64
       end

julia> t = SMALLSTRUCTURE(fill(1, 7)...);

julia> setproperty!(t, Symbol("SEEDMIN"), 100)
100

julia> t
SMALLSTRUCTURE(1, 1, 100, 1, 1.0, 1.0, 1.0)

You want to use setproperty!. Note that you have to use Symbols with setproperty!, so I convert the string to a Symbol.

1 Like
3

My issue with this though is that the string would be “SMALLSTRUCTURE.SEEDMIN” and setproperty!(Symbol(SMALLSTRUCTURE),Symbol(SEEDMIN),5) does not work so how can I also read in the name of the strucutre based off of the input string.

4

no, SMALLSTRUCTURE is the name of the type. You need an instance of that type, the t in that example above.

You should store the variables in that you need to change in a Dict which you can access with a String key, rather than trying to use a string to look up variables in the global scope

5

Wait so are you saying that I should not use a structure to store all of my data
and just use a Dict?

6

And would it not be possible to pass in t as the string?

7

Is the input saying “If x is a SMALLSTRUCTURE, then update it’s SEEDMIN with 100”?