By: Bruce Bahlmann - Contributing Author (your feedback is important to us!)

In rails development, you will often want to use basic arithmetic. While all these work as you would expect, rails doesn't handle results well - particularly those results which do not come in the form of a whole number. So, this post is all about handling rails results that come of the form of a fraction or what rails call them (floats).

Below, we break down various mathematical operations (beginning with division) and how to achieve the kind of results you want without having to hunt-n-peck your way through various incomplete rails posts to find what you are looking for:

[Division]

4/2
=> 2

1/2
=> 0

7/3
=> 2

Float(1)/2
=> 0.5

Float(7)/3
=> 2.33333333333333

(Float(7)/3).round(2) 
=> 2.33

3.6/1.2
=> 3

3.8/0.7
=> 5.42857142857143

(3.8/0.7).round(4) 
=> 5.4286

RECOMMENDED METHOD:
(Float x/y)
=> result that always observes fraction

Notice above, that when using a whole number as the dividend (top number) and the divisor (bottom number) the results will be truncated as if rails thought it were only working with integers (whole numbers). To resolve this, you need to declare the dividend as a float (see above) - but only if dividend and divisor are whole numbers. Note that if either the dividend or the divisor is a real number (float), rails properly states the results as a fraction (if any). To be safe, it is probably best to declare the dividend as a float to ensure rails properly produces a fraction when it is supposed to.

Multiplication:

[multiplication]

Common errors when working with numbers:

[can't convert Fixnum into String]

@survey["delta"] = (@survey.inviteListing.size - @survey.completedListing.size) +" is the difference"
=> "can't convert Fixnum into String"

USE Instead:
@survey["delta"] = "#{(@survey.inviteListing.size - @survey.completedListing.size)}" +" is the difference"

This is a work in progress.

This is a work in progress...

.

Can Birds-Eye.Net help you or your Company? Receive your Birds-Eye.Net articles and white papers hot off the presses by adding our RSS feed to your reader.

(C) Copyright Birds-Eye.Net, All rights reserved.
It is against the law to reproduce this content or any portion of it in any form without the explicit written permission of Birds-Eye Network Services, LLC. Federal copyright law (17 USC 504) makes it illegal, punishable with fines up to $100,000 per violation plus attorney's fees.