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 ? @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.
# File activesupport/lib/active_support/core_ext/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
Note that this doesn’t prevent a NoMethodError if you attempt to call a method that doesn’t exist on a valid object.
a = Article.new a.try(:author) #=> #<Author ...> nil.try(:doesnt_exist) #=> nil a.try(:doesnt_exist) #=> NoMethodError: undefined method `doesnt_exist' for #<Article:0x106c7d5d8>
This is on Ruby 1.8.7 patchlevel 174
a = Article.new a.try(:author) #=> #<Author ...> nil.try(:doesnt_exist) #=> nil a.try(:doesnt_exist) #=> nil
a.try(&:doesnt_exist) #=> Raises NoMethodError