Hands-On Design Patterns and Best Practices with Julia

Controlling write access to object fields

In order to manage write access to the fields of an object, we can extend the setproperty! function, in a similar way to how we did for read access.

Let's recall how the FileContent data type was designed:

mutable struct FileContent    path    loaded    contentsend

Suppose that we want to allow the user to switch to a different file by mutating the path field with a new file location. In addition to this, we want to prevent the loaded and contents fields from being changed directly using dot notation. To achieve that, we can extend the setproperty! function as follows:

function Base.setproperty!(fc::FileContent, s::Symbol, value)    if s === :path        ss = lstat(value)        setfield!(fc, :path, value) setfield!(fc, :loaded, ...