winking's Blog

Ruby exception Supporting tagline

ruby exception

Exception

  1. NoMemoryError

  2. ScriptError

    LoadError

    NotImplementedError

    SyntaxError

  3. SignalException

    Interrupt

  4. StandardError

    ArgumentError

    IOError

    EOFError

    IndexError

    LocalJumpError

    NameError

    NoMethodError

    RangeError

    FloatDomainError

    RegexpError

    RuntimeError

    SecurityError

    SystemCallError

    SystemStackError

    ThreadError

    TypeError

    ZeroDivisionError

  5. SystemExit

fatal

If we need to throw a Exception,we can use the exception class above ,or create one from StandardError.

We use begin,’rescue’,end,raise,ensure,retry,catch,throw to deal with Exception.

for example, put the code which will create Exception between begin,end. and the code after rescue, will deal with the Exception.such as:

open_file = File.open(open_file_name, "w")

begin

while data = socket.read(512)

open_file.write(data)

end

rescue SystemCallError

$stderr.print "IO failed: " + $!

open_file.close

File.delete(open_file_name)

raise

end

But as we all known , use $! is not a good way to controller the Exception, cause thewe can get this Exception everywhere. So we can create a variable for it.

If we want to know the kind of Exceptions, use exception.kind_of?

In many cases, we need to do sth , no matter resuce work or not, here we can use ensure,for example,

f = File.open("testfile")

begin

# .. what you want to do

rescue

# .. handle error

else

puts "OK"

ensure

f.close unless f.nil?

end

retry help us to retry the code, if it throws exception before.
raise ,to custom Exception

raise , it will throw a current exception,if not exist, throw a RunTimeError.

raise "information" , throw a exception with “information” info

raise ArgumentError, "information", custom the kind of Error and message for it .

catch and throw

def promptAndGet(prompt)

print prompt

res = readline.chomp

throw :quitRequested if res == "!"

return res

end

catch :quitRequested do

name = promptAndGet("Name: ")

end

here , if we get a ”!”,it will stop dealing with user’s input.

rails exception

There are two articles for rails exception, they may be good examples for us.

http://clark1231.iteye.com/blog/1446693

http://hlee.iteye.com/blog/353732

blog comments powered by Disqus

Published

15 May 2012

Tags