View Source Migrating from Lens 1

Migration is supposed to be easy.

Note that you can migrate one module at a time.

There are perhaps gotchas yet to be discovered.

1. Put use Lens2 at the top of any module that defines or uses lenses.

2. Code that makes lenses (Lens.key(:a)) need not be changed.

3. Replace the operations like Lens.to_list and Lens.map with their Lens2.Deeply equivalents. Note that you have to change the argument order:

    Lens.put(lens, container, value)     # Lens 1
    Deeply.put(container, lens, value)   # Lens 2

   Here is a list of changes:

    Lens.each(lens, container, f)         Deeply.each(container, lens, f)
    Lens.get_and_map(lens, container, f)  Deeply.get_and_update(container, lens, f)
    Lens.map(lens, container, f)          Deeply.update(container, lens, f)
    Lens.one!(lens, container)            Deeply.get_only(container, lens) or Deeply.one!(container, lens
    Lens.put(lens, container, v)          Deeply.put(container, lens, v)
    Lens.to_list(lens, container)         Deeply.get_all(container, lens) or Deeply.to_list(container, lens)

4. use Lens2 will import macros deflens and deflens_raw, so you don't have to change them. However, it also imports defmaker and def_raw_maker, which I prefer.

5. If you use TypedStruct and TypedStructLens, you have to add an alias Lens2.TypedStructLens to your existing modules. See the module documentation.