Sometimes it makes sense to treat errors as part of an application's "valid" flow of events. Meaning, expected errors should not necessarily make your code go crazy when random errors are raised.
With that in mind, I created a way to implement some kind of "Result Object" by rescuing StandardError instances and handling these errors gracefully.
class Gracefully
class << self
alias_method :handle, :new
end
attr_reader :error, :value
def initialize
@value = nil
@error = nil
begin
@value = yield
rescue => e
@error = e
end
end
def success?
error.nil?
end
def on_success
return self unless success?
result = yield(@value)
return result if result.is_a?(Gracefully)
Gracefully.handle { result }
end
def on_failure
return self if success?
result = yield(@error)
return result if result.is_a?(Gracefully)
Gracefully.handle { result }
end
end
In short, _ Gracefully _ is a wrapper for a result object– it’s either a success value or an error object.
result = Gracefully.handle { Order.find 999 }
In the example above, if order with id 999 does not exist, result.success? method will return false. Otherwise, true.
If result.success?is true, result.value will contain the successful value. Otherwise, result.error will hold the error object itself.
Whenever Gracefully.handle is called, it will return a Gracefully object. If you want to get the raw value, you can use result.value.
More Usage
result = Gracefully.handle { ComplicatedService.new(foo, bar).process }
if result.success?
# do success stuff
use_value(result.value)
else
# do failure stuff
log_error(result.error)
end
Chaining Usage
Gracefully.handle { SomeComplicatedService.new.call }.on_success do |val|
val.update!(column_name: 'stuff')
end
Gracefully.handle { SomeComplicatedService.new.call }.on_failure do |e|
do_whatever_you_wish_with_the_error(e)
end
By using this, I can be resilient in handling errors and be able to recover from failures in the process flow.
The post Handling Errors Gracefully appeared first on KatPadi's Point.
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