Ruby Set Variable If Nil

And even those speaking ruby quite fluently don t usually know the tiny little details.

Ruby set variable if nil. Variable empty while it works it doesn t seem very ruby like to me. In 99 of the cases if a local variable is missing you have a typo or someone forgot to declare that variable. Undefined instance variables are always nil so you want to check for that. Just like any other ruby object nil has a set of methods.

Global variable in class1 is 10 global variable in class2 is 10 ruby instance variables. Below i have my controller and it is quite annoying having to write the same line of code user city nil user city for every variable. There are plenty of options available. The resulting reddit quickly picked up on his definition which was fixed later and argued about s true meaning which isn t as obvious as many rubyists think.

In ruby on rails what s the difference actually. This spread to freenode s awesome ruby lang irc channel where. I m trying to set a variable conditionally in ruby. I ve come up with the following.

Instance variables begin with commat. Uninitialized instance variables have the value nil and produce warnings with the w option. I think it s more object oriented especially in a language like ruby where everything is an object and message exchange. Is the a more succinct way of expressing the above.

Do stuff when variable is nil end however i believe that the latter is a better option for two reasons. You should be aware that undefined instance variables will return nil. I need to set it if the variable is nil or empty 0 length string. In rubyists already use monadic patterns dave fayram made a passing reference to using to set a variable s value if its value were nothing false or nil in ruby.

What about instance variables. For many beginning rubyists especially those having experience in other programming languages such as java or c checking whether variable is nil may seem a little bit confusing. Here is an example showing the usage of instance variables. Try the safe navigator operator ruby 2 3 which only calls a method if the variable is not nil.

Let s evaluate their usefulness and potential problems that they bring to the table. I am not too familiar with creating my own methods but can i somehow create a shortcut to do something like this. Foo nil so watch out for that it might just happen that you misspelt the name of your instance variable or you forgot to initialize it. Memoirs of a software team leader read more.

September 11 2010 4 minute read tags.