Question

What is the difference between those syntax?
Is there any benefit with the first over the second?

agent = Mechanize.new

# first
agent.get(url) do |page|
work
end

#second
page = agent.get(url)

Which one should I use when and why?

Answer 1

The two ways of calling the get method end up doing the same thing. You can use it either way you like. The first way where it allows you to pass a block might be useful in writing more concise and/or readable code. Its up to you to choose whichever fits your need. Take for example;

agent = Mechanize.new

agent.get(url) do |page|
   item = page.forms.first do |form|
     form.fieldname = "foo"
   end.submit
   # do something with item
end

which reads better than

page = agent.get(url)
form = page.forms.first
form.fieldname = "foo"
item = agent.submit(form).body
#do something with item

Same case applies when doing Mechanize initialization. I prefer

@agent = Mechanize.new { |agent|
  agent.user_agent_alias = 'Mac Safari'
  agent.follow_meta_refresh = true
  agent.redirect_ok = true
}

to

@agent = Mechanize.new
@agent.user_agent_alias = 'Mac Safari'
@agent.follow_meta_refresh = true
@agent.redirect_ok = true

}