Structs... creating a struct without passing all variables

General Usage
1

hello guys,
I have defined a struct with 5 variables
then
I created one and I passed 3 out of 5 variables
now I am getting error
How do I define a struct without needing to define all variables

Thank you

2

You probably want to define a constructor with default arguments, like:

julia> struct MyType
           a
           b
           c
       end

julia> MyType(a, b) = MyType(a, b, "default value")
MyType

julia> MyType(1,2)
MyType(1, 2, "default value")
3

Okay… I will check it now and give you feedback
Thank you

4

It didnot work until
I declared my type as “mutable struct”
and
I also had to give all variable a zero value as an initial value
then
I worte

mystruct.x=50

look here please

![p33|690x401](upload://1t5SxtMZj1Dgw0uuBh7m5ZdZgKs.png)
5

p33
p331112×647 42.7 KB

6

I don’t think you understood my suggestion, here’s an example with your struct defintion:

# Define the struct - this will automatically provide a constructor that takes all fields
struct lineStruct2
    buses_line::Vector{Int}
    res_line::Float64
    ind_line::Float64
    imp_mag_line::Float64
    imp_angle_line::Float64
    p_line::Float64
    q_line::Float64
    state_line::String
end

# Define an outer constructor that only requires the first three inputs, using default values for the remaining inputs
lineStruct2(buses_line, res_line, ind_line) = lineStruct2(buses_line, res_line,
    ind_line, 0.0, 0.0, 0.0, 0.0, "overloaded")

# Test that it works
lineStruct2([1,2,3], 0.0, 0.0)
3 Likes
7

use Parameters.jl

8

I get an invalid redefinition

look at this pls

invalid
invalid1366×738 68.8 KB

9

I tried with both mutable and without it

10

I just pressed enter in the REPL and the error did not show again why is that ?

11

You have to restart Julia.

Also typenames should be CapitalCase (by convention). So call it LineStruct, not lineStruct.

1 Like
12

yes, it worked thank you …
now
when I type for example

L2=lineStruct2([1,2,3],10,10)

I get an error that L2 is undefined

Why ?!

13

That seems unlikely. It would help if you could give a MWE with code written in mono-spaced font

```
using backticks like the above
your code here
```

to help isolate the problem.

1 Like
14

I would highy recommend you read through the relevant section of the manual.

As @DNF says you cannot re-define types within the same Julia session:

julia> struct MyType
           a::Float64
       end

julia> struct MyType
           no_wait_I_changed_my_mind
       end
ERROR: invalid redefinition of constant MyType
Stacktrace:
 [1] top-level scope at REPL[2]:1

Therefore, once you’ve defined LineStruct you can only change that after restarting Julia. That’s also why in my example it was called LineStruct2, because LineStruct was already defined in the session when I created the MWE.

Can you restart Julia and run the following:

struct LineStruct
    buses_line::Vector{Int}
    res_line::Float64
    ind_line::Float64
    imp_mag_line::Float64
    imp_angle_line::Float64
    p_line::Float64
    q_line::Float64
    state_line::String
end

LineStruct(buses_line, res_line, ind_line) = LineStruct(buses_line, res_line,
    ind_line, 0.0, 0.0, 0.0, 0.0, "overloaded")

l2 = LineStruct2([1,2,3], 0.0, 0.0)

Note that as per @DNF’s suggestion I’ve capitalized LineStruct (the type) here, but lowercased l2 (an instance of the type).

This should work and do what you want.

1 Like
15

Thanks alot… it worked and I will check the link too now Thanks again