challenges with grails unique: true

Grails does not evaluate a unique constraint at GORM level but at the database level

    static constraints = {
        property unique: true
    }

This means that you would not get a grails.validation.ValidationException but a org.springframework.dao.DataIntegrityViolationException.

This means that

domainInstance.validate()

would not capture a duplicate "property"

Sometimes cron runs twice

I suspected cron was running twice. I confirmed by checking the system logs

grep CRON /var/log/syslog

Then I killed cron and restarted it

sudo /etc/init.d/cron stop
sudo /etc/init.d/cron start

Tail vs Less

Learnt a good chunk about less and tail from this site http://www.brianstorti.com/stop-using-tail/ 

Access child components in vue.js

Sending mail in unix with attachment

You would need to install sharutils

sudo apt-get install sharutils

Then run this

uuencode <path_to_file> <name_to_give_attachment> | mail -s "Subject" foo@example.com

Also see http://soamweird.blogspot.com/2016/03/sending-mail-in-unix.html

Sorting by type first then alphabetically

The script below ensures that items are sorted by type first then by alphabetical order.

The spaceship operator

Just ran into this and I thought it was really cool.

So the spaceship operator (<=>) delegates to the compareTo method:

assert (1 <=> 1) == 0
assert (1 <=> 2) == -1
assert (2 <=> 1) == 1
assert ('a' <=> 'z') == -1

For more checkout http://groovy-lang.org/operators.html