class Traject::TranslationMap
A TranslationMap
is basically just something that has a hash-like []
method to map from input strings to output strings:
translation_map["some_input"] #=> some_output
Input is assumed to always be string, output is either string or array of strings.
What makes it more useful than a stunted hash is it's ability to load the hash definitions from configuration files, either pure ruby, yaml, or java .properties file (not all .properties features may be supported, we use dot-properties gem for reading)
traject's `extract_marc` macro allows you to specify a :translation_map=>filename argument that will automatically find and use a translation map on the resulting data:
extract_marc("040a", :translation_map => "languages")
Or you can always create one yourself and use it how you like:
map = TranslationMap.new("languages")
In either case, TranslationMap
will look for a file named, in that example, `languages.rb` or `languages.yaml` or `languages.properties`, somewhere in the ruby $LOAD_PATH in a `/translation_maps` subdir.
-
Also looks for “/translation_maps” subdir in load paths, so for instance you can have a gem that keeps translation maps in ./lib/translation_maps, and it Just Works.
-
Note you do NOT supply the .rb, .yaml, or .properties suffix yourself,
it'll use whichever it finds (allows calling code to not care which is used).
Ruby files just need to have their last line eval to a hash. They file will be run through `eval`, don't do it with untrusted content (naturally)
You can also pass in a Hash for consistency to TranslationMap.new
, although I don't know why you'd want to.
## Special default handling
The key “__default__” in the hash is treated specially. If set to a string, that string will be returned by the TranslationMap
for any input not otherwise included. If set to the special string “__passthrough__”, then for input not mapped, the original input string will be returned.
This is most useful for YAML definition files, if you are using an actual ruby hash, you could just set the hash to do what you want using Hash#default_proc etc.
Or, when calling TranslationMap.new()
, you can pass in options over-riding special key too:
TranslationMap.new("something", :default => "foo") TranslationMap.new("something", :default => :passthrough)
## Output: String or array of strings
The output can be a string or an array of strings, or nil. It should not be anything else. When used with the translate_array!
method, one string can be replaced by multiple values (array of strings) or removed (nil)
There's no way to specify multiple return values in a .properties, use .yaml or .rb for that.
## Caching
Lookup and loading of configuration files will be cached, for efficiency. You can reset with `TranslationMap.reset_cache!`
## YAML example:
key: value key2: value2 multiple words fine key2b: "Although you can use quotes if you want: Or need." key3: - array - of - values look like this
## Alternatives `Traject::TranslationMap` provides an easy way to deal with the most common translation case: simple key-value stores with optional default values.
If you need more complex translation, you can simply use `#map!` or its kin to work on the `accumulator` in a block
# get a lousy language detection of any vernacular title require 'whatlanguage' wl = WhatLanguage.new(:all) to_field 'vernacular_langauge', extract_marc('245', :alternate_script=>:only) do |rec, acc| # accumulator is already filled with the values of any 880s that reference a 245 because # of the call to #extract_marc acc.map! {|x| wl.language(x) } acc.uniq! end
Within the block, you may also be interested in using:
-
a case-insentive hash, perhaps like [this one](github.com/junegunn/insensitive_hash)
-
a [MatchMap](github.com/billdueber/match_map), which implements pattern-matching logic similar to solrmarc's pattern files
Attributes
Public Class Methods
# File lib/traject/translation_map.rb, line 169 def initialize(defn, options = {}) if defn.kind_of? Hash @hash = defn elsif defn.kind_of? self.class @hash = defn.to_hash @default = defn.default else @hash = self.class.cache.lookup(defn) raise NotFound.new(defn) if @hash.nil? end if options[:default] @default = options[:default] elsif @hash.has_key? "__default__" @default = @hash["__default__"] end end
# File lib/traject/translation_map.rb, line 162 def reset_cache! cache.reset_cache! end
Protected Class Methods
We use dot-properties gem for reading .properties files, return a hash.
# File lib/traject/translation_map.rb, line 260 def self.read_properties(file_name) return DotProperties.load(file_name).to_h end
Public Instance Methods
# File lib/traject/translation_map.rb, line 187 def [](key) if self.default && (! @hash.has_key?(key)) if self.default == "__passthrough__" return key else return self.default end end @hash[key] end
Return a new TranslationMap
that results from merging argument on top of self. Can be useful for taking an existing translation map, but merging a few overrides on top.
merged_map = TranslationMap.new(something).merge TranslationMap.new(else) #... merged_map.translate_array(something) # etc
If a default is set in the second map, it will merge over the first too.
You can also pass in a plain hash as an arg, instead of an existing TranslationMap:
TranslationMap.new(something).merge("overridden_key" => "value", "a" => "")
# File lib/traject/translation_map.rb, line 245 def merge(other_map) default = other_map.default || self.default TranslationMap.new(self.to_hash.merge(other_map.to_hash), :default => default) end
Returns a dup of internal hash, dup so you can modify it if you like.
# File lib/traject/translation_map.rb, line 202 def to_hash dup = @hash.dup dup.delete("__default__") dup end
Run every element of an array through this translation map, return the resulting array. If translation map returns nil, original element will be missing from output.
If an input maps to an array, each element of the array will be flattened into the output.
If an input maps to nil, it will cause the input element to be removed entirely.
# File lib/traject/translation_map.rb, line 217 def translate_array(array) array.each_with_object([]) do |input_element, output_array| output_element = self.map(input_element) if output_element.kind_of? Array output_array.concat output_element elsif ! output_element.nil? output_array << output_element end end end
# File lib/traject/translation_map.rb, line 228 def translate_array!(array) array.replace( self.translate_array(array)) end