Module: AppInfo::Tryable

Included in:
Object
Defined in:
lib/app_info/core_ext/object/try.rb

Overview

:nodoc:

Instance Method Summary collapse

Instance Method Details

#try(method_name = nil, *args, &block) ⇒ Object

:method: try

:call-seq:

try(*a, &b)

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.name if @person

try calls can be chained:

@person.try(:spouse).try(:name)

instead of

@person.spouse.name if @person && @person.spouse

try will also return nil if the receiver does not respond to the method:

@person.try(:non_existing_method) # => nil

instead of

@person.non_existing_method if @person.respond_to?(:non_existing_method) # => 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 in case of argument mismatch.

If try is called without arguments it yields the receiver to a given block unless it is nil:

@person.try do |p|
  ...
end

You can also call try with a block without accepting an argument, and the block will be instance_eval’ed instead:

@person.try { upcase.truncate(50) }

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.



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# File 'lib/app_info/core_ext/object/try.rb', line 72

def try(method_name = nil, *args, &block)
  if method_name.nil? && block_given?
    if block.arity.zero?
      instance_eval(&b)
    else
      yield self
    end
  elsif respond_to?(method_name)
    public_send(method_name, *args, &block)
  end
end

#try!(method_name = nil, *args, &block) ⇒ Object

:method: try!

:call-seq:

try!(*a, &b)

Same as #try, but raises a NoMethodError exception if the receiver is not nil and does not implement the tried method.

"a".try!(:upcase) # => "A"
nil.try!(:upcase) # => nil
123.try!(:upcase) # => NoMethodError: undefined method `upcase' for 123:Integer



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# File 'lib/app_info/core_ext/object/try.rb', line 96

def try!(method_name = nil, *args, &block)
  if method_name.nil? && block_given?
    if block.arity.zero?
      instance_eval(&block)
    else
      yield self
    end
  else
    public_send(method_name, *args, &block)
  end
end