Equatable and HashSets Demo

EquatableAndHashSetDemo.ps1

using namespace System.Collections.Generic

class Pet {
  [string]$Name
  [string]$Type

  hidden [int] GetHashCode() {
    $uniqueString = $this.Name + $this.Type
    return $uniqueString.GetHashCode()
  }
  hidden [bool] Equals($other) {
    return $this.GetHashCode() -eq $other.GetHashCode()
  }
}

class Person {
  [string]$Name
  [HashSet[Pet]]$Pets = @{}

  hidden [int] GetHashCode() {
    return $this.Name.GetHashCode()
  }
  hidden [bool] Equals($other) {
    return $this.GetHashCode() -eq $other.GetHashCode() -and $this.Pets.SetEquals($other.Pets)
  }
  hidden static [Person] op_Addition([Person] $person, [Pet] $pet) {
    if (-not $person.Pets.Add($pet)) {
      throw "$($pet.Name) [$($Pet.Type)] already belongs to $($person.Name)"
    }
    return $person
  }
}

class House {
  [string]$Address
  [HashSet[Person]]$People = @{}

  hidden [int] GetHashCode() {
    return $this.Address.GetHashCode()
  }
  hidden [bool] Equals($other) {
    return $this.GetHashCode() -eq $other.GetHashCode() -and $this.People.SetEquals($other.People)
  }
  hidden static [House] op_Addition([House] $house, [Person] $person) {
    if (-not $house.People.Add($person)) {
      throw "$($person.Name) already lives here"
    }
    return $house
  }
}


#Tests:
$HouseA = [house]@{Address = 'testaddress' }
$HouseB = [house]@{Address = 'testaddress' }
$HouseC = [house]@{Address = 'differentAddress' }
$HouseD = [house]@{Address = 'testaddress' }

$John = [Person]@{Name = 'John' }
$JohnClone = [Person]@{Name = 'John' }
$Jane = [Person]@{Name = 'Jane' }

$Spot = [Pet]@{Name = 'Spot'; Type = 'Dog' }
$Kitty = [Pet]@{Name = 'Kitty'; Type = 'Cat' }

$HouseA -eq $HouseB #True
$HouseA -ne $HouseC #Because the address is different

$HouseA += $John #Add John to HouseA
try {
  $HouseA += $John #Errors that John already is here
} catch {
  Write-Warning $_.Exception.InnerException.Message
}
try {
  $HouseA += $Spot #Cannot Add pets to the house directly. You could have logic here that adds the pet to all people in the house.
} catch {
  Write-Warning $_.Exception.InnerException.Message
}

$HouseA -ne $HouseB #True because John lives in one but not the other
$HouseB += $John #Add John to HouseB
$HouseA -eq $HouseB #True because now John lives in both

$John -eq $JohnClone #True because their names are the same
$John -ne $Jane #True because they have different names
$John += $Spot #Add Spot to John
$John -ne $JohnClone #Untrue now because even tho same names, different pets
try {
  $John += $Spot #Errors that John already has spot
} catch {
  Write-Warning $_.Exception.InnerException.Message
}


$HouseD += $JohnClone
$HouseA -ne $HouseD #False because even though John and JohnClone have the same name, they have different pets, which results in them not equaling each other on the hashset comparison