In Corona (and Lua in general), variables aren’t declared explicitly before you use them.  When  Lua sees a variable name that you haven’t declared as local, it starts looking up the chain of scopes until it reaches the Global namespace (_G).  If it gets there, it creates a key in the _G table with your variable name.

This little trick (shown to me by my friend Chris Blackwell) makes Corona tell you whenever this happens.  Sometimes it’s fine, but most of the time you’ll find a typo (as I did in the Particle Candy library).   I even found that loading the built-in JSON library causes it to check for a global called “Chipmunk.”  Granted, Chipmunk isn’t a typo, but it is accessing a variable that doesn’t exist.  This can happen if you’re check to see if something has been loaded or not.  In those cases this warning can be ignored.

So, put this in your app’s main.lua, run your app in the simulator and watch the console output.  You might just find a problem you didn’t know you had.

Note: You only want this in debug builds.  You could wrap it with a check for running on the simulator, but the best bet is to just remove it before building your final version.

local globalsmeta = {
__index = function(table, key)
print("!!! access to nonexistent global variable "..tostring(key).."n"..debug.traceback())
end
}
setmetatable(_G, globalsmeta)

This works by adding a metatable to the Global namespace to call this function whenever you access an unknown key in its table.

The post ProTip for Corona: Finding Typos appeared first on Ben Sharpe.

I’ve recently been trying out different editors as I can see the end of the road for TextMate from where I’m sitting.   I really wanted to be super-awesome and finally learn vi or emacs, but despite several attempts, my brain hasn’t really latched onto them like it did when TM came onto the scene.

Now there’s SublimeText 2 (in beta) which is starting to be the editor that TM wanted to be when it grew up.  There’s still a lot of funky things with it, but I can see the potential.  Not to mention it’s cross platform like the ancient gods vi and emacs.   I suppose that’s really just icing on the cake because I rarely leave my home platform for reasons other than duress (Windows) or curiosity (Linux).

The one thing I really missed from TM was the ability to launch the CoronaSDK simulator from the editor.   It’s fantastic to be able to edit a file and hit a button and have it fire up the simulator and then start reloading the simulator each time the file changes. (actually the simulator does that work for you)  I took a look at the Corona bundle for TM and found quite a few lines of AppleScript that are doing the work (i kid not).

tl;dr

In Sublime, select “Tools > Build System > New Build System…”

This opens up a new text file.  Copy and paste this into it:

{
"osx" : {
"cmd": ["/Applications/CoronaSDK/Corona Simulator.app/Contents/MacOS/Corona Simulator","main.lua"]
},
"windows" : {
"cmd": ["C:\Program Files\Corona Labs\Corona SDK\Corona Simulator.exe","main.lua"]
},
"file_regex": "^[ ]*File "(...*?)", line ([0-9]*)",
"working_dir": "${project_path:${folder}}",
"selector": "source.lua"
}

By setting the working_dir to the project folder and specifying ‘main.lua’ as the file, you can launch the simulator for a project no matter what file you happen to be looking at (or in what subfolder).

Save the file as “CoronaSDK.sublime-build”

1. Go to your Corona project
2. Open a file to edit
3. Select  Tools > Build System > CoronaSDK
4. Press Command-B
5. profit!

For Reference,  custom build system files are usually stored in the following locations:

OS X: ~/Library/Application Support/Sublime Text 2/Packages/User

Windows: %APPDATA%/Sublime Text 2/Packages/User

The post CoronaSDK and SublimeText2 Build System appeared first on Ben Sharpe.

1. Build the app using  File > Build > Amazon/Kindle…
2. On the Fire, go to Settings and tap More
3. Tap Device
4. Turn ON “Allow Installation of Applications — from unknown sources”
5. Plug in a Micro-B usb cable into the Fire and the other into your computer (in this case a MacBook Air)
6. The Kindle should be showing up on your desktop
7. Copy the .apk file generated by Corona onto the Kindle (I’m not sure that it makes a difference where — I used the “downloads” folder)
8. Eject the Kindle from the Mac
9. On the Kindle you’ll need a File management application installed (I used “ES File Explorer” because it was free and had the most reviews)
10. Use the File manager to find your app and tap it to install it
11. Profit!

The post CoronaSDK: Building and installing on a Kindle Fire appeared first on Ben Sharpe.

Want to know if a file exists before you use it?

Lately, I’ve been wanting something a little more dynamic in my projects for opening various Scenes (think Director, but not).   I needed a way of looking to see if a file existed or not before I tried to load it up.  Here’s the result:

function fileExists(fileName, base)
  assert(fileName, "fileName is missing")
  local base = base or system.ResourceDirectory
  local filePath = system.pathForFile( fileName, base )
  local exists = false
 
  if (filePath) then -- file may exist. won't know until you open it
    local fileHandle = io.open( filePath, "r" )
    if (fileHandle) then -- nil if no file found
      exists = true
      io.close(fileHandle)
    end
  end
 
  return(exists)
end

Typical usage:

if fileExists("myGame.lua") then
  -- do something wonderful
end

If the file does not exist, the CoronaSDK library function system.pathForFile() returns nil.  It also returns a Warning in the console, which can be safely ignored.

By default it checks your app’s asset directory (system.ResourceDirectory), however, if you’d like to check if a file you created exists you can pass in an alternative base path like so:

if fileExists("some_file.txt", system.DocumentsDirectory) then
  -- do something wonderful
end

The three valid options for base path are:

1. system.ResourceDirectory
2. system.DocumentsDirectory
3. system.TemporaryDirectory

The post CoronaSDK: How to know if a file exists? appeared first on Ben Sharpe.

Update April 2011: I now use the Heroku Plus gem to manage these accounts.

I have several Heroku accounts that I need to switch between for clients. I’ve been doing it by hand for a while, and then I remembered that I could just write a bash script to make a command for my forgetful brain.

The basic steps are:

• >heroku keys:clear
• >rm ~/.heroku/credentials
• >heroku list

So, my little bash script is:

#!/bin/bash
 
heroku keys:clear && rm ~/.heroku/credentials && heroku list

do a quick
>chmod 775 switch_heroku

and now I can switch with that simple command.
This is on OS X. Probably very similar on Linux. No idea on windows.

The post Switching Heroku Accounts appeared first on Ben Sharpe.

The Basics

While I could talk you through the whole enchilada. Robby Russell over at Planet Argon has already done this. He’s done an excellent job of updating this guide over the years, and it’s usually the first place I go with a new installation. Someday, I’m sure I’ll have it memorized.

Ruby

While you can use the built-in ruby on Snow Leopard, I like to look forward to the day when we’re all 30% faster simply by deploying on Ruby 1.9. I use it in development for that very reason. However, most clients like to use Ruby Enterprise Edition because it’s so efficient and stable. Therefore, we need to switch between versions easily. Enter the Ruby Version Manager.

>sudo gem install rvm

RVM not only keeps your system clean, but it allows for easy switching between versions of ruby.

For most cases I like to use the 1.9.3 as my default ruby.

>rvm install 1.9.3
>rvm use 1.9.3 --default

But I also like to have Ruby 2.0 around for the speed.

>rvm install 2.0

Gems

Make sure rubygems is up to date.

>gem update --system

Edit your ~/.gemrc file to contain something like the following:

---
gem: --no-ri --no-rdoc
:benchmark: false
:backtrace: false
:update_sources: true
:verbose: true
:bulk_threshold: 1000
:sources:
- http://gems.rubyforge.org

The most important reason to do this is for that second line. It stops gem from installing the ri and rdoc documentation which I never use anyway. This speeds up gem installation considerably.

Since we’re using RVM which keeps separate gem directories for each version of Ruby, you’ll need to install a few gems. (Even if you went through this from Robby’s instructions)

The most basic gems first:

>gem install rails mongrel

and then the gems for the DB:

>gem install hirb wirble

>gem install haml compass thin cheat

>cheat strftime

require 'irb/completion'
 
# History
#require 'irb/ext/save-history'  #wirble does history
IRB.conf[:SAVE_HISTORY] = 100
IRB.conf[:HISTORY_FILE] = "#{ENV['HOME']}/.irb-save-history"
 
# Wirble is a plugin to colorize your irb, it's installed from a gem (gem install -y wirble)
require 'rubygems'
begin
  # load wirble
  require 'wirble'
 
  # start wirble (with color)
  Wirble.init
  Wirble.colorize
rescue LoadError => err
  warn "Couldn't load Wirble: #{err}"
end
 
ARGV.concat ["--readline", "--prompt-mode", "simple"]
 
# autoindent of code while typing it
IRB.conf[:AUTO_INDENT]=true
 
# Log to STDOUT if in Rails && use HIRB if available
if ENV.include?('RAILS_ENV') && !Object.const_defined?('RAILS_DEFAULT_LOGGER')
  begin
    require 'hirb'
    Hirb.enable
  rescue LoadError => err
    warn "No Hirb: #{err}"
  end
  require 'logger'
  RAILS_DEFAULT_LOGGER = Logger.new(STDOUT)
end
 
# Easily print methods local to an object's class
class Object
  def local_methods
    (methods - Object.instance_methods).sort
  end
end
 
# copy a string to the clipboard
def pbcopy(string)
  `echo "#{string}" | pbcopy`
  string
end

# Rails 1.0+
alias ss='script/server'
alias sc='script/console'
alias sg='script/generate'
alias sp='script/plugin'
alias tdl='tail -f log/development.log'
# Rails 2.0+
alias sdb='script/dbconsole'
# Rails 3.0+
alias sr='script/rails'
# Passenger
alias rr='touch tmp/restart.txt'
 
# Useful Git aliases
alias gst='git status'
alias gl='git pull'
alias gp='git push'
alias gdm='git diff | mate'
alias gc='git commit -v'
alias gcam='git commit -v -a -m'
alias gb='git branch --color'
alias gba='git branch --color -a'
alias gaa='git add .'
alias gco='git checkout'
alias gsp='git svn dcommit'
alias gsl='git svn rebase'
alias gsf='git svn fetch'