Show HN: Learn Ruby by Example with Challenges(learneroo.com)
learneroo.com
Show HN: Learn Ruby by Example with Challenges
http://www.learneroo.com/modules/61/nodes/338
6 comments
Thanks. The challenge was meant as a way to review the different booleans, instead of 'real code'. I added a warning, but I'll see if other code would be better.
The biggest problem is that the interesting part about this challenge (different precendence) is rather advanced to beginners and is _not even touched_ in the preceding parts.
> The words 'and' and 'or' should not be used for boolean comparisons, they are intended to be used to join two separate clauses such as "render 'template' and return" in rails.
Is that true? Because I found a bug in our code recently that was in a line like
render_error and return
where the return was never getting called because render_error returned false. I don't understand why you would write code like that when you could simply write:
render_error
return
and not have to deal with thinking about whether render_error could ever return a falsey value.
Is that true? Because I found a bug in our code recently that was in a line like
render_error and return
where the return was never getting called because render_error returned false. I don't understand why you would write code like that when you could simply write:
render_error
return
and not have to deal with thinking about whether render_error could ever return a falsey value.
I don't know Ruby, but this caught my eye:
true.class #=> TrueClass
false.class #=> FalseClass
TrueClass and FalseClass aren't exactly "classes" in the usual sense - for instance, `TrueClass.new` throws a NoMethodError.
Under the hood, true and false are singletons - `(1 == 1).object_id` will always be 20. At least in MRI / YARV, that makes booleans much cheaper in terms of memory (a single pointer vs. a pointer + an RObject struct) but means that they don't have their own instance methods.
Keeping the classes separate makes it possible to metaprogram additional behavior onto true and false - for instance, the `blank?` method added by ActiveSupport.
Under the hood, true and false are singletons - `(1 == 1).object_id` will always be 20. At least in MRI / YARV, that makes booleans much cheaper in terms of memory (a single pointer vs. a pointer + an RObject struct) but means that they don't have their own instance methods.
Keeping the classes separate makes it possible to metaprogram additional behavior onto true and false - for instance, the `blank?` method added by ActiveSupport.
Don't rely on that ;)
Ruby 1.9.3
> (1==1).object_id => 2
> (1!=1).object_id => 0
Ruby 1.9.3
> (1==1).object_id => 2
> (1!=1).object_id => 0
Ah, made me think of the good ol' days => http://rubyquiz.com/
Although this is definitely more tutorial-ish.
Although this is definitely more tutorial-ish.
The design of the site looks strange to my eyes. Colors and fonts doesn't make sense. I'm no expert on design so I can't explain why.
If you use Sublime Text it looks pretty familiar in the context of ruby code.
I don't think that was in reference to the syntax highlighting.
Great! Diving head first into Ruby so this will come in handy.
Is there anything like this for Javascript?
Since it looks like this was pretty popular, I'll make one for Javascript too. Meanwhile, check out the original LearnXinYminutes.
I only looked at Ruby Basics, but here's my feedback:
The challenge is to solve: 'true and 0 && !nil and 3 > 2', but this is not a real-life application.
The words 'and' and 'or' should not be used for boolean comparisons, they are intended to be used to join two separate clauses such as "render 'template' and return" in rails.
Comparing a number and bang-nil is not good code. This could actually come to be if you were doing something like: "object.value && !object.value". However, you wouldn't ever want to hardcode "0 && !nil". If you were really checking for nil, you should use "!object.nil?"
I'm afraid that these challenges will teach bad code techniques to newbies who don't know the difference. But again, as someone with more familiarity with Ruby, I think these types of challenges are fun, but if that is the goal there is no need for the tutorial beforehand.