Class: Diff::LCS::DiffCallbacks

Inherits:
Object
  • Object
show all
Defined in:
lib/diff/lcs/callbacks.rb

Overview

This will produce a compound array of simple diff change objects. Each element in the #diffs array is a hunk or hunk array, where each element in each hunk array is a single Change object representing the addition or removal of a single element from one of the two tested sequences. The hunk provides the full context for the changes.

diffs = Diff::LCS.diff(seq1, seq2)
# This example shows a simplified array format.
# [ [ [ '-',  0, 'a' ] ],   # 1
#   [ [ '+',  2, 'd' ] ],   # 2
#   [ [ '-',  4, 'h' ],     # 3
#     [ '+',  4, 'f' ] ],
#   [ [ '+',  6, 'k' ] ],   # 4
#   [ [ '-',  8, 'n' ],     # 5
#     [ '-',  9, 'p' ],
#     [ '+',  9, 'r' ],
#     [ '+', 10, 's' ],
#     [ '+', 11, 't' ] ] ]

There are five hunks here. The first hunk says that the a at position 0 of the first sequence should be deleted ('-'). The second hunk says that the d at position 2 of the second sequence should be inserted ('+'). The third hunk says that the h at position 4 of the first sequence should be removed and replaced with the f from position 4 of the second sequence. The other two hunks are described similarly.

Use

This callback object must be initialised and is used by the Diff::LCS#diff method.

cbo = Diff::LCS::DiffCallbacks.new
Diff::LCS.lcs(seq1, seq2, cbo)
cbo.finish

Note that the call to #finish is absolutely necessary, or the last set of changes will not be visible. This callback also supports a block mode which automatically calls #finish.

result = Diff::LCS::DiffCallbacks.new { |cbo| Diff::LCS.lcs(seq1, seq2, cbo) }

Simplified Array Format

The simplified array format used in the example above can be obtained with:

require 'pp'
pp diffs.map { |e| e.map { |f| f.to_a } }

Direct Known Subclasses

ContextDiffCallbacks

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize ⇒ DiffCallbacks

:yields: self



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# File 'lib/diff/lcs/callbacks.rb', line 101

def initialize # :yields: self
  @hunk = []
  @diffs = []

  return unless block_given?

  begin
    yield self
  ensure
    finish
  end
end

Instance Attribute Details

#diffs ⇒ Object (readonly)

Returns the difference set collected during the diff process.



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# File 'lib/diff/lcs/callbacks.rb', line 99

def diffs
  @diffs
end

Instance Method Details

#discard_a(event) ⇒ Object 



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# File 'lib/diff/lcs/callbacks.rb', line 120

def discard_a(event)
  @hunk << Diff::LCS::Change.new("-", event.old_position, event.old_element)
end

#discard_b(event) ⇒ Object 



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# File 'lib/diff/lcs/callbacks.rb', line 124

def discard_b(event)
  @hunk << Diff::LCS::Change.new("+", event.new_position, event.new_element)
end

#finish ⇒ Object

Finalizes the diff process. If an unprocessed hunk still exists, then it is appended to the diff list.



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# File 'lib/diff/lcs/callbacks.rb', line 116

def finish = finish_hunk

#match(_event) ⇒ Object 



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# File 'lib/diff/lcs/callbacks.rb', line 118

def match(_event) = finish_hunk