Thursday, September 8, 2011

Navigation methods in Rails

I may not always feel like coding, but most of the time if I sit down to code I get warmed up and quickly forget I didn't feel like coding. Today was one of those days. I didn't feel like coding, but I took a look at my to-do list and figured "Hey, I can at least knock out some of this easy CSS stuff, right?" I try to live by a code of "Rails every day".

With that said, here's a little problem I've got.

Here's how I currently have a Back link written in my Menu partial:

<%= link_to 'Back', characters_path %>

The problem is, I render this partial on every page, and so the Back link shouldn't always point to characters_path. I thought an easy solution to this would be to write the code like so:

<%= link_to 'Back', :back %>

This returns the user to the last page viewed, which is closer to what I want, but then I run into some irritating navigational issues. Say you were looking at a Character's Items, and created a new Item, then hit the Back button once it was created. Since I'm rendering the form in the Items view page, it simply takes the user back to the previous view, showing a form with blank fields. So here's my question:

Is there an easier way to handle this? A better method than :back? Should I simply make two versions of the menu partial, each with a separate back link? I don't think I'll need more than two. The menu partial rendered when viewing a Character will want to point back to characters_path, whereas every other page (Items, Skills, and so forth) will need to point back to the Character view page. Maybe I'm overthinking this, considering it's just an extra partial, but I'm thinking there might be a better way to handle this. Imagine if I wanted five different menu partials, or twenty? I think it's better to think of more abstract solutions that can be applied to multiple scenarios.

Wednesday, September 7, 2011

More has_one model work in Rails

When it comes to coding, it seems like I've got good days, bad days, and frustrating days. Sometimes the Venn diagrams of these days overlap quite a bit. Take today for example.

I've been coding now for a little over 2 hours and I've finally gotten a problem straightened out. If you'll recall, I was attempting to build a Background for a Character, have it show up in my menu partial, and editable from there. I had a method that would build models with a has_many relationship to Character, but Background will have a has_one relationship and it was proving a bit trickier. I've more or less got it straightened out now (at least it's working on my local machine) so I've thrown it up on Heroku.

Manticore on Heroku

I've also done some more work, simplifying the data that's actually displayed in the view, while still allowing users to manipulate that data with an edit action. My reasoning is a user may always want to know what his total Armor Class is, but how often do you need to know what your Deflection modifier is? Not often, that's how! So basically, if you're rarely going to need it, why display it all the time? I think eventually I'd like to have an arrow users can click on that might expand that information, while displaying the bare minimum by default. I'm not sure what I'd use for this, but it sounds like a problem for Javascript.

Also, don't mind those saving throws! They refuse to work. What a lazy model! This merits a bit of examination. And I actually just realized it's not working when creating a new character on Heroku. Thanks, Heroku!

Still, it feels good to have this problem figured out. I've been wrestling with it for a while, and now I can move on to wrestle with other, more interesting problems! Like this mysterious SAVING THROW problem that's arisen. What could be going on here?

Absolutely LOVE crossing things off my list. Although I appear to have added several more. As usual.

Monday, September 5, 2011

Difference between build_model and create_model in Rails

I keep a note pad with features I want to add, things I need to fix and other reminders to myself whenever I'm coding an application. I've got a few methods defined in my models that will calculate totals. Needless to say, these methods aren't going to do anything but complain if the data fields they use to calculate a total either don't exist or aren't integers. What to do?

Validation to the rescue! But I had a problem. A minor problem. The models I speak of all belong to a main Character model. Take my Initiative model for example. It belongs_to Character, and Character has_one Initiative. I have a few fields in Initiative: :dex, :misc, and :speed. These refer to a Character's Dexterity modifier, any miscellaneous modifiers and how many feet that Character can move in a round. So I have this method defined in Initiative.rb:

def total
  dex + misc

This way, I can simply call in a view and Rails will calculate the total for me. Cool, right? And this is where validation comes in handy. However, here's the issue I had. My validation worked, but it was showing an error BEFORE any data had been entered. Definitely better than not working, or allowing a user to enter a B instead of an 8, but I'd rather not show an error message if no error has been made. So what was the solution?

First, the validation I wrote, in my Initiative model.

validates_presence_of :dex, :misc, :speed
validates_numericality_of :dex, :misc, :speed

This all looks good. I suspected the error was in the way my new method was written in Intiatives controller, but I couldn't figure it out, so I asked for help on StackOverflow. User m_x was kind enough to point me in the right direction.

def new
  @character = Character.find(params[:character_id])
  @initiative = @character.create_initiative(params[:initiative])

This bit of code was the culprit. Easy enough to fix, though.

def new
  @character = Character.find(params[:character_id])
  @initiative = @character.build_initiative(params[:initiative])

It turns out the reason my validation was being called before a user had entered any data is because the create method creates a new object and attempts to save it. In this case, it wasn't saving because it failed the validation, because nothing had been entered yet. On the other hand, the build method creates a new object, but does NOT save it. Easy enough to remember! As an added bonus, this gives me some ideas on how to tackle another problem I've been thinking about.

This mistake feels like something I should have known before hand, considering how much time I've spent reading through the Rails API, but I have a hard time holding on to information until it becomes practical. But now that I've used this, and cemented exactly what the difference is between build_model and create_model, I won't make the same mistake again.

One less thing, right?