Class: Object
- Inherits:
- BasicObject
- Extended by:
- MissingHandler
- Defined in:
- lib/droiuby/support/object/duplicable.rb,
lib/droiuby/support/thread.rb,
lib/droiuby/support/autoload.rb,
lib/droiuby/support/to_query.rb,
lib/droiuby/support/object/try.rb,
lib/droiuby/support/object/blank.rb,
lib/droiuby/support/object/deep_dup.rb,
lib/droiuby/support/object/to_param.rb,
lib/droiuby/support/object/to_query.rb,
lib/droiuby/support/object/acts_like.rb,
lib/droiuby/support/object/inclusion.rb,
lib/droiuby/support/object/instance_variables.rb
Overview
– Most objects are cloneable, but not all. For example you can’t dup nil
:
nil.dup # => TypeError: can't dup NilClass
Classes may signal their instances are not duplicable removing dup
/clone
or raising exceptions from them. So, to dup an arbitrary object you normally use an optimistic approach and are ready to catch an exception, say:
arbitrary_object.dup rescue object
Rails dups objects in a few critical spots where they are not that arbitrary. That rescue is very expensive (like 40 times slower than a predicate), and it is often triggered.
That’s why we hardcode the following cases and check duplicable? instead of using that rescue idiom. ++
Instance Method Summary collapse
-
#acts_like?(duck) ⇒ Boolean
A duck-type assistant method.
-
#blank? ⇒ Boolean
An object is blank if it’s false, empty, or a whitespace string.
-
#deep_dup ⇒ Object
Returns a deep copy of object if it’s duplicable.
-
#duplicable? ⇒ Boolean
Can you safely dup this object?.
-
#in?(*args) ⇒ Boolean
Returns true if this object is included in the argument.
-
#instance_values ⇒ Object
Returns a hash with string keys that maps instance variable names without “@” to their corresponding values.
-
#instance_variable_names ⇒ Object
Returns an array of instance variable names as strings including “@”.
-
#presence ⇒ Object
Returns object if it’s
present?
otherwise returnsnil
. -
#present? ⇒ Boolean
An object is present if it’s not
blank?
. -
#to_param ⇒ Object
Alias of
to_s
. -
#to_query(key) ⇒ Object
Converts an object into a string suitable for use as a URL query string, using the given
key
as the param name. -
#try(*a, &b) ⇒ Object
Invokes the public method whose name goes as first argument just like
public_send
does, except that if the receiver does not respond to it the call returnsnil
rather than raising an exception. -
#try!(*a, &b) ⇒ Object
Same as #try, but will raise a NoMethodError exception if the receiving is not nil and does not implemented the tried method.
- #with_large_stack(stack_size_kb = 64, &block) ⇒ Object
Methods included from MissingHandler
Instance Method Details
#acts_like?(duck) ⇒ Boolean
A duck-type assistant method. For example, Active Support extends Date to define an acts_like_date?
method, and extends Time to define acts_like_time?
. As a result, we can do x.acts_like?(:time)
and x.acts_like?(:date)
to do duck-type-safe comparisons, since classes that we want to act like Time simply need to define an acts_like_time?
method.
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# File 'lib/droiuby/support/object/acts_like.rb', line 7 def acts_like?(duck) respond_to? :"acts_like_#{duck}?" end |
#blank? ⇒ Boolean
An object is blank if it’s false, empty, or a whitespace string. For example, ”, ‘ ’, nil
, [], and {} are all blank.
This simplifies:
if address.nil? || address.empty?
…to:
if address.blank?
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# File 'lib/droiuby/support/object/blank.rb', line 14 def blank? respond_to?(:empty?) ? empty? : !self end |
#deep_dup ⇒ Object
Returns a deep copy of object if it’s duplicable. If it’s not duplicable, returns self
.
object = Object.new
dup = object.deep_dup
dup.instance_variable_set(:@a, 1)
object.instance_variable_defined?(:@a) #=> false
dup.instance_variable_defined?(:@a) #=> true
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# File 'lib/droiuby/support/object/deep_dup.rb', line 13 def deep_dup duplicable? ? dup : self end |
#duplicable? ⇒ Boolean
Can you safely dup this object?
False for nil
, false
, true
, symbol, and number objects; true otherwise.
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# File 'lib/droiuby/support/object/duplicable.rb', line 24 def duplicable? true end |
#in?(*args) ⇒ Boolean
Returns true if this object is included in the argument. Argument must be any object which responds to #include?
. Usage:
characters = ["Konata", "Kagami", "Tsukasa"]
"Konata".in?(characters) # => true
This will throw an ArgumentError if the argument doesn’t respond to #include?
.
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# File 'lib/droiuby/support/object/inclusion.rb', line 10 def in?(*args) if args.length > 1 puts "Calling #in? with multiple arguments is" \ " deprecated, please pass in an object that responds to #include? instead." args.include? self else another_object = args.first if another_object.respond_to? :include? another_object.include? self else raise ArgumentError.new 'The single parameter passed to #in? must respond to #include?' end end end |
#instance_values ⇒ Object
Returns a hash with string keys that maps instance variable names without “@” to their corresponding values.
class C
def initialize(x, y)
@x, @y = x, y
end
end
C.new(0, 1).instance_values # => {"x" => 0, "y" => 1}
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# File 'lib/droiuby/support/object/instance_variables.rb', line 12 def instance_values Hash[instance_variables.map { |name| [name[1..-1], instance_variable_get(name)] }] end |
#instance_variable_names ⇒ Object
Returns an array of instance variable names as strings including “@”.
class C
def initialize(x, y)
@x, @y = x, y
end
end
C.new(0, 1).instance_variable_names # => ["@y", "@x"]
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# File 'lib/droiuby/support/object/instance_variables.rb', line 25 def instance_variable_names instance_variables.map { |var| var.to_s } end |
#presence ⇒ Object
Returns object if it’s present?
otherwise returns nil
. object.presence
is equivalent to object.present? ? object : nil
.
This is handy for any representation of objects where blank is the same as not present at all. For example, this simplifies a common check for HTTP POST/query parameters:
state = params[:state] if params[:state].present?
country = params[:country] if params[:country].present?
region = state || country || 'US'
…becomes:
region = params[:state].presence || params[:country].presence || 'US'
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# File 'lib/droiuby/support/object/blank.rb', line 37 def presence self if present? end |
#present? ⇒ Boolean
An object is present if it’s not blank?
.
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# File 'lib/droiuby/support/object/blank.rb', line 19 def present? !blank? end |
#to_param ⇒ Object
Alias of to_s
.
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# File 'lib/droiuby/support/object/to_param.rb', line 3 def to_param to_s end |
#to_query(key) ⇒ Object
Converts an object into a string suitable for use as a URL query string, using the given key
as the param name.
Note: This method is defined as a default implementation for all Objects for Hash#to_query to work.
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# File 'lib/droiuby/support/to_query.rb', line 8 def to_query(key) require 'cgi' unless defined?(CGI) && defined?(CGI::escape) "#{CGI.escape(key.to_param)}=#{CGI.escape(to_param.to_s)}" end |
#try(*a, &b) ⇒ Object
Invokes the public method whose name goes as first argument just like public_send
does, except that if the receiver does not respond to it the call returns nil
rather than raising an exception.
This method is defined to be able to write
@person.try(:name)
instead of
@person ? @person.name : nil
try
returns nil
when called on nil
regardless of whether it responds to the method:
nil.try(:to_i) # => nil, rather than 0
Arguments and blocks are forwarded to the method if invoked:
@posts.try(:each_slice, 2) do |a, b|
...
end
The number of arguments in the signature must match. If the object responds to the method the call is attempted and ArgumentError
is still raised otherwise.
If try
is called without arguments it yields the receiver to a given block unless it is nil
:
@person.try do |p|
...
end
Please also note that try
is defined on Object
, therefore it won’t work with instances of classes that do not have Object
among their ancestors, like direct subclasses of BasicObject
. For example, using try
with SimpleDelegator
will delegate try
to the target instead of calling it on delegator itself.
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# File 'lib/droiuby/support/object/try.rb', line 41 def try(*a, &b) if a.empty? && block_given? yield self else public_send(*a, &b) if respond_to?(a.first) end end |
#try!(*a, &b) ⇒ Object
Same as #try, but will raise a NoMethodError exception if the receiving is not nil and does not implemented the tried method.
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# File 'lib/droiuby/support/object/try.rb', line 51 def try!(*a, &b) if a.empty? && block_given? yield self else public_send(*a, &b) end end |
#with_large_stack(stack_size_kb = 64, &block) ⇒ Object
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# File 'lib/droiuby/support/thread.rb', line 2 def with_large_stack(stack_size_kb = 64, &block) result = nil t = Thread.with_large_stack(&proc{result = block.call}) t.join result end |