Visitor pattern: Difference between revisions
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julia example
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* [https://www.codeproject.com/Articles/588882/TheplusVisitorplusPatternplusExplained Code Project - The Visitor Pattern Explained]
<br>
=={{header|Julia}}==
<syntaxhighlight lang="julia">abstract type CarElementVisitor end
struct CarElementDoVisitor <: CarElementVisitor end
struct CarElementPrintVisitor <: CarElementVisitor end
abstract type CarElement end
struct Body <: CarElement end
struct Engine <: CarElement end
struct Wheel <: CarElement
name::String
Wheel(str::String) = new(str)
end
struct Car <:CarElement
elements::Vector{CarElement}
Car() = new([Wheel("front left"), Wheel("front right"),
Wheel("rear left"), Wheel("rear right"),
Body(), Engine()])
end
accept(e::CarElement, visitor::CarElementVisitor) = visit(visitor, e)
function accept(car::Car, visitor::CarElementVisitor)
for element in car.elements
accept(element, visitor)
end
visit(visitor, car)
end
visit(v::CarElementDoVisitor, e::Body) = println("Moving my body.")
visit(v::CarElementDoVisitor, e::Car) = println("Starting my car.")
visit(v::CarElementDoVisitor, e::Wheel) = println("Kicking my $(e.name) wheel.")
visit(v::CarElementDoVisitor, e::Engine) = println("Starting my engine.")
visit(v::CarElementPrintVisitor, e::Body) = println("Visiting body.")
visit(v::CarElementPrintVisitor, e::Car) = println("Visiting car.")
visit(v::CarElementPrintVisitor, e::Wheel) = println("Visiting $(e.name) wheel.")
visit(v::CarElementPrintVisitor, e::Engine) = println("Visiting engine.")
car = Car()
accept(car, CarElementPrintVisitor())
println()
accept(car, CarElementDoVisitor())
</syntaxhighlight>{{out}} Same as Phix entry.
=={{header|Phix}}==
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