Alternatives to Exceptions

iteration

Alternatives to Exceptions

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• Multiple return values in failures can be helpful -
• Represent a process as an object “Download Provisionment” - This is a really interesting idea…. “MessageSend.new” - would actually handle a lot of the issues in the SMS interface concept we’ve been talking through.
• “It’s tempting to raise an exception every time you get an answer you don’t like. But exception handling interrupts and obscures the flow of your business logic. Consider carefully whether a situation is truly unusual before raising an Exception.”
• Diagnostics- don’t fail SO aggressively early that you don’t capture the diagnostics.

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Examples of when to not "fail fast":

1. test suites

Sometimes you just need a way to proceed through steps and have the system tell you what parts succeeded and what parts failed

Sideband data

When communication failures without resorting to exceptions, we need a sideband: a secondary channel of communication for reporting meta-information about the status and disposition of a process.

Multiple return values

hehe, this reminds me of stuff I do in javascript

• ruby supports multiple return values in the form of array splatting. in JS, you could do this with destructuring

  def foo
  result = 42
  success = true
  [result, success]
  end

  result, success = foo
  puts "#{success ? 'succeeded' : 'failed'}; result #{result}"

Or you can use an open struct

def foo OpenStruct.new(:result => 42, :status => :success) end 

Output parameters

Caller-supplied fallback strategy

• if we're not sure we want to terminate the execution of a long process by raising an exception, we can inject a failure policy into the process

  def make_user_accounts(host, failure_policy=method(:raise))
  # ...
  rescue => error
  failure_policy.call(error)
  end

  def provision_host(host, failure_policy)
  make_user_accounts(host, failure_policy)
  end

  policy = lambda { |e| puts e.message }
  provision_host("192.168.1.123", policy)

Picks

JP:

• https://github.com/xotahal/react-native-motion
• https://github.com/fram-x/FluidTransitions
• https://github.com/callstack/react-native-testing-library

John:

Slack Video Calling + Collaboration