lll

lll() is used in debugging to display an expression and its value.

Motivation

One of the most basic tools in debugging is printing out the values of variables (or other expressions) during program execution:

    puts user_name

Sometimes you need to label these values so you know what they’re referring to, especially if you’re outputting a lot of them:

    puts "user_name = #{message}"

lll() does the labelling automatically:

    lll{'user_name'}

The expression is passed as a string inside a block. It’s useful to create a text editor macro that outputs lll{''} and leaves the cursor inside the apostrophes.

Other benefits

Output goes to standard output and the Rails log (if available).

Output is displayed in reverse video, so it’s easy to pick out from the log or console.

lll() uses inspect to output the expression. It outputs Enumerable members (except strings) on separate lines.

Outputting additional text

Sometimes you need to include some other string, along with the label and value:

    puts "After polling the queue, user_name = #{user_name}"

You can pass a string to lll() to print a string:

    lll("After polling the queue"){'user_name'}

And because lll() outputs in reverse video, and to the Rails log, it can be useful to simply print a string without an expression:

    lll "After read_user"

Files

Class Index

lll

Motivation

Other benefits

Outputting additional text

Copyright