Hands-On Design Patterns and Best Practices with Julia

Identifying traits

The next step is to assign data types to these traits. Conveniently, Julia allows us to bulk-assign traits to an entire subtype tree using the <: operator in the function signature:

# Default behavior is illiquidLiquidityStyle(::Type) = IsIlliquid()# Cash is always liquidLiquidityStyle(::Type{<:Cash}) = IsLiquid()# Any subtype of Investment is liquidLiquidityStyle(::Type{<:Investment}) = IsLiquid()

Let's take a look at how we can interpret these three lines of code:

• We have chosen to make all the types illiquid by default. Note that we could have done this the other way around and made everything liquid by default. This decision is arbitrary and depends on the specific use case.
• We have chosen to make all the subtypes ...