module VestalVersions::Changes::HashMethods

Instance methods included into Hash for dealing with manipulation of hashes in the specific format of ActiveRecord::Base#changes.

Public Instance Methods

append_changes(changes) click to toggle source

When called on a hash of changes and given a second hash of changes as an argument, append_changes will run the second hash on top of the first, updating the last element of each array value with its own, or creating its own key/value pair for missing keys. Resulting non-unique array values are removed.

Example

first = {

"first_name" => ["Steve", "Stephen"],
"age" => [25, 26]

} second = {

"first_name" => ["Stephen", "Steve"],
"last_name" => ["Richert", "Jobs"],
"age" => [26, 54]

} first.append_changes(second) # => {

"last_name" => ["Richert", "Jobs"],
"age" => [25, 54]

}

# File lib/vestal_versions/changes.rb, line 87
def append_changes(changes)
  changes.inject(self) do |new_changes, (attribute, change)|
    new_change = [new_changes.fetch(attribute, change).first, change.last]
    new_changes.merge(attribute => new_change)
  end.reject do |attribute, change|
    change.first == change.last
  end
end
append_changes!(changes) click to toggle source

Destructively appends a given hash of changes onto an existing hash of changes.

# File lib/vestal_versions/changes.rb, line 97
def append_changes!(changes)
  replace(append_changes(changes))
end
prepend_changes(changes) click to toggle source

Appends the existing hash of changes onto a given hash of changes. Relates to the append_changes method in the same way that Hash#reverse_merge relates to Hash#merge.

# File lib/vestal_versions/changes.rb, line 104
def prepend_changes(changes)
  changes.append_changes(self)
end
prepend_changes!(changes) click to toggle source

Destructively prepends a given hash of changes onto an existing hash of changes.

# File lib/vestal_versions/changes.rb, line 109
def prepend_changes!(changes)
  replace(prepend_changes(changes))
end
reverse_changes() click to toggle source

Reverses the array values of a hash of changes. Useful for reversion both backward and forward through a record's history of changes.

# File lib/vestal_versions/changes.rb, line 115
def reverse_changes
  inject({}){|nc,(a,c)| nc.merge!(a => c.reverse) }
end
reverse_changes!() click to toggle source

Destructively reverses the array values of a hash of changes.

# File lib/vestal_versions/changes.rb, line 120
def reverse_changes!
  replace(reverse_changes)
end