Cannot assign struct as a dictionary value

New to Julia
1

Hi!
I have a simple struct to store some data:

struct Gene
    name::String
    exonarray::Array
    pi::Int64
    pf::Int64
    is_reverse::Bool
    #note::String 
end

I then get some data from a file and generate an object:

myname = "Gene_1"
myarray = []
mypi = 1
mypf = 1500
myrev = false

mygene = Gene(myname,myarray,mypi,mypf,myrev)

Then, I want to push this new object into a dictionary, using a string as key.

mydict = Dict
mydict[myname] = mygene

This raises an error:

ERROR: LoadError: MethodError: no method matching setindex!(::Type{Dict}, ::Gene, ::String)

What am I doing wrong? How do I assign a struct as a Dictionary value?

2

Change that to mydict = Dict().

Or even better:

mydict = Dict{String, Gene}()
6 Likes
3

if I try

mydict  = Dict()
#or
mydict = Dict{String,Gene}()

I get a slightly different error:

ERROR: LoadError: MethodError: no method matching getindex(::Gene, ::Int64)
4

What code are you running to get this error? The code you posted above works with either mydict = Dict() or mydict = Dict{String,Gene}():

julia> struct Gene
           name::String
           exonarray::Array
           pi::Int64
           pf::Int64
           is_reverse::Bool
           #note::String
       end

julia> myname = "Gene_1"
"Gene_1"

julia> myarray = []
Any[]

julia> mypi = 1
1

julia> mypf = 1500
1500

julia> myrev = false
false

julia> mygene = Gene(myname,myarray,mypi,mypf,myrev)
Gene("Gene_1", Any[], 1, 1500, false)

julia> mydict = Dict{String,Gene}()
Dict{String,Gene}()

julia> mydict[myname] = mygene
Gene("Gene_1", Any[], 1, 1500, false)

julia> mydict
Dict{String,Gene} with 1 entry:
  "Gene_1" => Gene("Gene_1", Any[], 1, 1500, false)
1 Like
5

Big confusion. I modified the variable names a bit, (like my_dict to mydict, and my_gene to mygene).
Now the code works as it should. Thanks for your help!
What is the effect of the ()? What is the difference between Dict and Dict()?

6

Dict is a type and Dict() creates an object of that type (in this case, of the type Dict{Any,Any}, which is a concrete subtype of Dict). It’s like the difference between Int64 (a type) and 5 (a value of that type).

3 Likes
7

For better performance, you should pick a concrete type for the exonarray field, like Array{Int64,1} instead of Array.

2 Likes