如何在 Julia 中 initialize/construct 深层嵌套结构？

Question

我想创建一些更深层次的嵌套结构。 Setfield.jl 包似乎足以填满它们。但是我正在努力初始化（空）结构以稍后迭代地填充它们。这些结构看起来像：

struct Bands
   B0::String
   B1::String
   B2::String
   B3::String
   B4::String
   B5::String
   .
   .
   .
   B25::String
end 


struct Masks
   mask1::Bands
   mask2::Bands
   mask3::Bands
   mask4::Bands
   mask5::Bands
   mask6::String
end

我已经尝试过内部构造函数并按照此处所述https://docs.julialang.org/en/v1/manual/constructors/#Incomplete-Initialization-1. It seems that I have to set all values before like described at https://jw3126.github.io/Setfield.jl/stable/intro/。如何初始化嵌套结构，在这种情况下一次初始化 131 个值？

Answer 1

例如，您可以创建默认构造函数，这些构造函数只为您以后可以更新的所有字段放置空对象

julia> struct Bands
           B0::String
           B1::String

           # Create a constructor that puts an empty String ("") for each field
           Bands() = new(("" for _ in 1:length(fieldnames(Bands)))...)

           # Define a vararg constructor
           Bands(args...) = new(args...)
       end

julia> struct Masks
           mask1::Bands
           mask2::Bands

           # Create a constructor that puts an empty Bands (Bands()) for each field
           Masks() = new((Bands() for _ in 1:length(fieldnames(Masks)))...)

           # Define a vararg constructor
           Masks(args...) = new(args...)
       end

julia> masks = Masks()
Masks(Bands("", ""), Bands("", ""))

julia> using Setfield

julia> masks = @set masks.mask1 = Bands("hello", "world") # Set a field of masks
Masks(Bands("hello", "world"), Bands("", ""))

julia> masks = @set masks.mask2.B0 = "hello" # Set a field of masks.mask2
Masks(Bands("hello", "world"), Bands("hello", ""))

Answer 2

对于您使用 Parameters.jl 的场景，代码会更简洁（此外，由于 String 是不可变的，因此您的 Bands struct 需要可变。

using Parameters

@with_kw mutable struct Bands
    B0::String = ""
    B1::String = ""
end

@with_kw struct Masks
    mask1::Bands = Bands()
    mask2::Bands = Bands()
end

通过这种方式，您的代码干净、可读，并且您不需要定义大量的构造函数。

如何在 Julia 中 initialize/construct 深层嵌套结构？

How to initialize/construct deep nested structs in Julia?

constructor

struct

initialization

julia