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Attaching array to existing Ruby method

Posted on 2011-03-21
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Last Modified: 2012-05-11
Neophyte has another question. I understand arrays and there purpose and am able to work with arrays adding and deleting information using the irb and prompt through the Mac terminal. What I am trying to do is connect an array to an existing ruby file that already has the class established and is producing the results. Basically, I would like to be able to push new objects through the method using an array.
# NewDeviceClass
#device
#nickname : old home pc
# status  : active
# type    : windows_pc
class NewDevice
    attr_accessor :device_name
      attr_accessor :device_status
      attr_accessor :device_type

  def output
  puts "This device has a nickname of #{device_name}, type of #{device_type}, and is #{device_status}."

  end

end

if __FILE__ == $0
dn = NewDevice.new
dn.device_name = "new device"
dn.device_status = "active"
dn.device_type = "windows pos"
dn.output

a = ["device_type1", "device_type2"]
end

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Question by:neophyteScripter
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4 Comments
 

Author Comment

by:neophyteScripter
ID: 35183250
basically, I need to create a for loop and push newdevices into the main method statement
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Expert Comment

by:kristinalim
ID: 35183463
There are a lot of options if you want to loop. I use Array#each a lot -- it is able to handle iteration on the collection most simply.

# Call whatever you use to get the array of NewDevice objects.
new_devices = NewDevice.find(:all)

# Perform a block on each member of the collection.
# new_device becomes the current member of the collection.
new_devices.each do |new_device|
  new_device.output
  # ... maybe other code you want to execute
end

# Alternatively, you can pass a reference to the object method to be called.
new_devices.each(&:output)

# You can also do everything straight away.
NewDevice.find(:all).each(&:output)

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Author Comment

by:neophyteScripter
ID: 35183761
can you go into more detail, pretend i have no clue what you are talking about. Thanks
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Accepted Solution

by:
kristinalim earned 2000 total points
ID: 35184064
# You implied you already have a way of coming up with the objects you
# need to process. Assign this collection of objects to a local variable, say
# "new_devices". So "new_devices" at this point will be the array of objects.
new_devices = NewDevice.find(:all)

# The Ruby Array has a method Array#each that allows us to perform a
# block on each member of the array. It basically handles iteration for us so
# we no longer have to do the usual
#    for (int i = 0; i < length ; i ++)
# logic.

# Option 1 (IMHO preferred) among many more
# So we call the each method on the array and pass a block with one argument.
# What this will do is iterate through the array, and for each member call the block
# passing the member to the block. Ie, the current member is accessed using the
# variable "new_device" while inside the block.
new_devices.each do |new_device|
  # "new_device" at this point has been set to be the current member of the array
  new_device.output
  # ... maybe other code you want to execute
end

# Option 2 among many more
# Maybe a clearer way of illustrating its effect:
def something_to_perform_on_new_device(new_device)
  new_device.output
end
i = 0
begin
  something_to_perform_on_new_device(new_devices[i])
  i += 1
end while i < new_devices.length

# Option 3 among many more
# Good if you need to call only one method on the objects.
# This alternative form of calling the Array#each method calls the
# NewDevice#output method for each member of the array.
new_devices.each(&:output)

# Extra:
# If you don't want to have to store the array of NewDevice objects, you can
# just join the return values together:
NewDevice.find(:all).each(&:output)
# instead of:
new_devices = NewDevice.find(:all)
new_devices.each(&:output)

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