00_try_and_endtry.md

Try and Endtry statement

we may recive some errors in our program. for example:

println($this_var_not_found)

output:

VariableError:
    undefined variable $this_var_not_found

or:

# undefined function
printlgdfgfd(^)

output:

NameError: undefined "printlgdfgfd"

they are errors.

but how to handle errors?

we can handle errors with try-endtry statement.

look at this example:

try handle_error
    println($somevar)
endtry

goto after_error

label handle_error

println('some errors raised')

label after_error

when you write code between try <label-name> ... endtry, errors will not raised in them and if an error is raised, that label where passed to try command will run. actually, we say to the Loza to don't show error to user and do that thing I'm saying you instead of default error showing.

Note: you can ue keyword end instead of endtry. It is not different.

how to access raised error data?

when error is raised in try statement, error data will put in mem (^):

try handle_error
    println($somevar)
endtry

goto after_error

label handle_error

$ex = ^ # copy mem (^) to $ex variable (this includes information about raised error)
println($ex) # output: VariableError: undefined variable $somevar

label after_error

The raised error data has more properties. This is a Class object. You will learn about classes in next sections.

try error
    gfgdhf
endtry

label error

$ex = ^ # raised error
println($ex->type) # output: VariableError
println($ex->message) # output: undefined variable $not_found
println($ex->file_path) # output: /path/to/script.loza
println($ex->line_number) # output: 2