Dealing properly with scope; came from:combine array(string) to string?

Ruby
1

In much of my code, I’ve built an Array object before a block for
scope reasons. Is this common practice?

b = %w|a b c d e|
a = [] #instantiation
b.each {|i| a << i*2}
puts a

Todd

2

You can usually use inject or collect to eliminate the a = [] line.
For example:

b = %w[a b c d e]
a = b.collect {|i| i * 2 }

Also, I would caution against using the variable i as anything but a
loop counter.

Regards,
Dan

3

On Thu, Mar 20, 2008 at 6:14 PM, Daniel F. [email protected]
wrote:

You can usually use inject or collect to eliminate the a = [] line.
For example:

b = %w[a b c d e]
a = b.collect {|i| i * 2 }

Unless you have a method that doesn’t return an array (i.e. something
other than map/collect). Sometimes you have to build the array inside
the iterator. I was just wondering if this was common practice.

Also, I would caution against using the variable i as anything but a
loop counter.

For production code, I agree. But, I think even then, I wouldn’t use
“i”.

Todd

4

On 21.03.2008 08:14, Todd B. wrote:

On Thu, Mar 20, 2008 at 6:14 PM, Daniel F. [email protected] wrote:

You can usually use inject or collect to eliminate the a = [] line.
For example:

b = %w[a b c d e]
a = b.collect {|i| i * 2 }

Unless you have a method that doesn’t return an array (i.e. something
other than map/collect). Sometimes you have to build the array inside
the iterator. I was just wondering if this was common practice.

Yes, that’s perfectly ok. Often you can also use a variant using
#inject, like

irb(main):003:0> b = %w[a b c d e]
=> [“a”, “b”, “c”, “d”, “e”]
irb(main):004:0> b.inject([]){|ar,el| ar << el*2}
=> [“aa”, “bb”, “cc”, “dd”, “ee”]

But that would be silly in this case since there is #map / #collect.

Kind regards

robert