I noticed in some code that Chet and I were writing that, as Smalltalkers, we tend to write really
tiny methods. Here's a patch of code to show what I mean. Pay no attention to what it does, just
look at how it looks.
def filesUnderManagement
names = (Dir.entries(@directoryName).select { | each | ! (/.bak/ =~ each) }).sort
names.reject { |each| FileTest.directory?(sourceName(each)) }
end
def archiveFiles
Dir.entries(@directoryName + '/archive').reject { | each | /^\./ =~ each }.sort.reverse
end
def backup
timeString = Time.now.strftime("%Y%m%d%H%M%S")
filesUnderManagement.each { | each | backupFile(each, timeString)}
end
def backupFile (fileName, timeString)
File.syscopy(sourceName(fileName), archiveName("#{fileName}.#{timeString}"))
end
def sourceName(fileName)
@directoryName + '/' + fileName
end
def archiveName(fileName)
@directoryName + '/archive/' + fileName
end
def restore (timeString)
restoreFiles(filesToRestore(timeString))
end
def restoreFiles(fileList)
fileList.each { | each | restoreFile(each) }
end
def restoreFile(fileName)
short = shortName(fileName)
File.syscopy(archiveName(fileName), sourceName(short))
end
def shortName(fileName)
pattern.match(fileName)[1]
end
def timeStamp(fileName)
pattern.match(fileName)[2]
end
def pattern
/(.*)\.(.*)/
end
In this whole program, a code manager we're working on, the longest method is this:
def findFirstOccurences(names)
current = ''
firstOccurrences = []
names.each do | each |
short = shortName(each)
if (short != current)
current = short
firstOccurrences << each
end
end
firstOccurrences
end
That's 12 lines long and to me it is way too long.
I see very little Ruby code where the average method length is just a couple of lines. I suspect
it's because it's so hard to find methods in a source file that we instinctively have as few as
possible. Clearly there are techniques one could use to make things better: we could alphabetize the
methods or arrange them in other ways. But the problem remains.
I think that part of the power of Smalltalk comes from the fact that the methods are all separate. A
Smalltalk browser has a pane listing just the method names, typically alphabetically (or possibly
grouped, alpha inside each group). When you click on a method in the list pane, that method appears.
You can look at it, edit it, save it, look at another, and so on.
At first when you use Smalltalk, it seems choppy as you have to keep clicking around to see what's
going on, and in a text window you can sort of do that with your eyes. But take a look at these
methods from the program we're writing. I'm not claiming that the names are perfect yet -- this is a
work in progress. But read my pretend throughts below and see if you can get what I /like/ about
tiny methods:
def restore (timeString)
restoreFiles(filesToRestore(timeString))
end
hmm, OK, he does a restore by restoring all the files to restore, based on the time string. I wonder
how he restores a file ...
def restoreFiles(fileList)
fileList.each { | each | restoreFile(each) }
end
OK, he goes through them all and restores each one ... how does he do that?
def restoreFile(fileName)
short = shortName(fileName)
File.syscopy(archiveName(fileName), sourceName(short))
end
Oh, I see, he is copying the archived file back to the source file.
(You have to know here that we are saving the Ruby file abc.rb as abc.rb.20020110164900 in our code
manager: we've appended a time stamp to the file name. That's not clear here. It should be.)
I wonder how he decides which file to restore ...
def filesToRestore(timeString)
findFirstOccurences(olderFiles(timeString))
end
OK, he takes the first occurrence of the files older than the time string ..
def olderFiles(timeString)
archiveFiles.select { |each | timeStamp(each) < timeString }
end
And so on.
Now most of us who read larger methods are used to doing the reverse. We look at a big blob of code
and figure out little chunks of it. Then maybe we comment the code or make a note or just leave the
figuring out to the next person.
Tiny methods -- when you get used to them -- are IME /much/ easier to write and to work with.
Editor-based languages like Ruby, Java, C++, encourage longer methods because we have to search with
our eyes to figure things out.
What does this mean? I don't know. I think it might mean that a browser for Ruby or Java or C++
would be really good. Visual Age for Java is really wonderful in the hands of people who learn to
work in the browser mode.
Or maybe ... it doesn't mean anything. The comments here will perhaps tell me.
Ronald E Jeffries
http://www.XProgramming.com
http://www.objectmentor.com
I'm giving the best advice I have. You get to decide whether it's true for you.