Ruby Exception Handling

I. Common ruby exception information:

Exception name	Common Causes	How to throw
RuntimeError	Default exception thrown by raise	Raise
NoMethodError	The corresponding method cannot be found for the object.	A = Oject. new A. jackmethod
NameError	The interpreter encounters an identifier that cannot be parsed as a variable or method name.	A = jack
IOError	Read closed streams, write read-only streams, or similar operations	STDIN. puts ("cannot write ")
Errno: error	File IO-related errors	File. open (-10)
TypeError	The method accepts parameters that cannot be processed.	A = 3 + "abc"
ArgumentError	An error occurred while passing the number of parameters.	Def o (x) endO (1, 2, 3)

 

Ii. Format

Refer to java exception handling.

try{  -------------- begin}catch(){  ---------rescue }finally{  ---------ensure}   ----------------end

Possible exception information may be contained between begin and end.

Specify the exception following rescue. The default value can be used by default. Rescue is paired with else. else does not specify an exception or has no exception.

Ensure is equivalent to finally in java and is not explained much.

Two important variables: $! : Exception description, $ @: Location of the exception.

Let's look at an example:

If _ FILE _ = $0 a = 10 B = 20 c = 0 begin ad = a/B ac = a/c rescue puts "exception # {$ !}, Location: # {$ @} "else puts" no exception "ensure puts" enters class finally zone "endend

Execution result:
Exception divided by 0, Location: exception. rb: 15: in '/' exception. rb: 15
Enter the class finally Area

3. Saving exception information to variables

Use: rescue => e

Print: puts e. to_s
Use the preceding example to replace rescue with the following:

Rescue => e puts "has an exception # {$ !}, Location: # {$ @} "puts e. to_s + "....."

Execution result:

Exception divided by 0, Location: exception. rb: 15: in '/' exception. rb: 15
Divided by 0 .....
Enter the class finally Area