Class: Spider::Model::IdentityMapper

Inherits:
Object
  • Object
show all
Defined in:
lib/spiderfw/model/identity_mapper.rb

Overview

The IdentityMapper, when in use, will hold a reference to each object; the mapper will coordinate with it to ensure that each object of the same model with the same primary keys will point to the same Ruby object. This may or may not be what you need: the IdentityMapper can be set globally by assigning an instance to #Spider::Model.identity_mapper=, or for a block of code by passing a block to the initializer.

Instance Method Summary collapse

Constructor Details

#initialize(&proc) ⇒ IdentityMapper

If passed a block, will activate the IdentityMapper, yield, and then deactivate it.



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# File 'lib/spiderfw/model/identity_mapper.rb', line 13

def initialize(&proc)
    @objects = {}
    @pks = {}
    if (proc)
        prev_im = Spider::Model.identity_mapper
        Spider::Model.identity_mapper = self
        begin
            yield self
        ensure
            Spider::Model.identity_mapper = prev_im
        end
    end
end

Instance Method Details

#delete(klass, obj_id) ⇒ Object 



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# File 'lib/spiderfw/model/identity_mapper.rb', line 138

def delete(klass, obj_id)
    pks = @pks[obj_id]
    return unless pks && @objects[klass]
    @objects[klass].delete(pks)
    @pks.delete(obj_id)
end

#get(model, values = nil, set_loaded = false) ⇒ Object

Get an instance of model with given values. Values must contain all of model’s primary keys. If an object with the same primary keys is found, it will be used; otherwise, a new instance will be created. In any case, the given values will be set on the object, before it is returned.

FIXME: refactor avoiding set_loaded



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# File 'lib/spiderfw/model/identity_mapper.rb', line 33

def get(model, values=nil, set_loaded=false)
    
    if !values && model.is_a?(BaseModel)
        curr = has?(model)
        return curr ? curr : put(model)
    end
    
    @objects[model] ||= {}
    pks = {}
    has_pks = false
    model.primary_keys.each do |k| 
        # dereference integrated primary keys
        v = (k.integrated? && values[k.integrated_from.name]) ? 
            values[k.integrated_from.name].get(k.integrated_from_element) :
            values[k.name]
        has_pks = true if v
        pks[k.name] = model.prepare_value(k, v)
    end
    normalize_pks(model, pks)
    unless has_pks
        raise IdentityMapperException, "Can't get #{model} from IdentityMapper without all primary keys, #{values.inspect} given"
    end
    pks.extend(HashComparison)
    current = @objects[model][pks]
    obj = nil
    if current
        obj = current
    else
#                Spider.logger.debug("GETTING NEW #{model} FROM #{pks.inspect}")
        obj = model.new(pks)
        #@objects[model][pks] = obj
    end
    # obj = (@objects[model][pks] ||= model.new(pks))
    pks.each{ |k, v| obj.element_loaded(k) }
    values.reject{|k,v| model.elements[k].primary_key? }.each do |k, v|
        v = get(v) if v.is_a?(BaseModel)
        if set_loaded
            obj.set_loaded_value(k, v)
        else
            obj.set(k, v)
        end
    end
#            Spider::Logger.debug("RETURNING #{obj.class} #{obj.object_id}")
    return obj
end

#has?(obj) ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/spiderfw/model/identity_mapper.rb', line 130

def has?(obj)
    pks = {}
    obj.class.primary_keys.each{ |key| pks[key.name] = obj.get(key) }
    pks = normalize_pks(obj.class, pks)
    pks.extend(HashComparison)
    @objects[obj.class] && @objects[obj.class][pks]
end

#normalize_pks(model, keys) ⇒ Object 



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# File 'lib/spiderfw/model/identity_mapper.rb', line 150

def normalize_pks(model, keys)
    model_pks = model.primary_keys.map{ |k| k.name }
    model_pks.each do |k|
        if keys[k] && keys[k].is_a?(BaseModel)
            keys[k] = keys[k].class.primary_keys.length > 1 ? keys[k].primary_keys : keys[k].primary_keys[0]
        end
    end
    keys.keys.each do |k|
        keys.delete(k) unless model_pks.include?(k)
    end
    keys
end

#put(obj, check = false, fail_if_exists = false) ⇒ Object

Puts an object into the identity mapper. If check is true, it will first check if the object exists, and if found merge it with the given obj; if check is false, if a object with the same primary keys exists it will be overwritten.



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# File 'lib/spiderfw/model/identity_mapper.rb', line 82

def put(obj, check=false, fail_if_exists=false)
    return nil unless obj
    return obj if obj._no_identity_mapper
    if (obj.is_a?(QuerySet))
        obj.each_current_index{ |i| obj[i] = put(obj[i], check) }
        return obj
    else
        return obj if @pks[obj.object_id]
        raise IdentityMapperException, "Can't get without all primary keys" unless obj.primary_keys_set?
        pks = {}
        obj.class.primary_keys.each{ |key| pks[key.name] = obj.get(key) }
        pks = normalize_pks(obj.class, pks)
        pks.extend(HashComparison)
        @objects[obj.class] ||= {}
        if (check && (existent = @objects[obj.class][pks]) && existent.object_id != obj.object_id)
            #debugger if fail_if_exists
            raise IdentityMapperException, "A different instance of the same object #{obj.inspect} already exists in the identity mapper" if fail_if_exists
            existent.merge!(obj)
            return existent
        else
            @objects[obj.class][pks] = obj
            @pks[obj.object_id] = pks
            traverse(obj)
            uow = Spider::Model.unit_of_work
            uow.add(obj) if uow && !uow.running?
            return obj
        end
    end
end

#put!(obj) ⇒ Object 



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# File 'lib/spiderfw/model/identity_mapper.rb', line 125

def put!(obj)
    put(obj, true, true)
end

#reset ⇒ Object 



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# File 'lib/spiderfw/model/identity_mapper.rb', line 145

def reset
    @objects = {}
    @pks = {}
end

#traverse(obj, check = false, fail_if_exists = false) ⇒ Object 



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# File 'lib/spiderfw/model/identity_mapper.rb', line 112

def traverse(obj, check=false, fail_if_exists=false)
    obj.class.elements_array.each do |el|
        next unless obj.element_has_value?(el)
        next unless el.model?
        subs = obj.get(el)
        subs = [subs] unless subs.is_a?(Enumerable)
        subs.each do |sub|
            put(sub, check, fail_if_exists) if sub && sub.primary_keys_set? && has?(sub).object_id != sub.object_id
        end
    end
    
end