|song| Not documented in Pickaxe Book

[Sam'l B]

Pickaxe Book (2nd Ed.), P. 49, 2nd example, line 3:

@songs.find {|song| title == song.name }

I can't find a definition of the "|song|" construction in the book.
It is intuitively obvious that it is a variable, and a sort of
"catcher's mitt" for the output of the method "@songs.find" -- and acts
that way for all other example in the book that I can find.

What I _can't_ find, though, is a discussion of the construction -- or
did I miss it somewhere?

Sam Bassett

 

[Timothy Hunter]

Pickaxe Book (2nd Ed.), P. 49, 2nd example, line 3:

@songs.find {|song| title == song.name }

I can't find a definition of the "|song|" construction in the
book. It is intuitively obvious that it is a variable, and a sort of
"catcher's mitt" for the output of the method "@songs.find" -- and
acts that way for all other example in the book that I can find.

What I _can't_ find, though, is a discussion of the construction
-- or did I miss it somewhere?

Sam Bassett

In the Pickaxe 2nd Ed., look at the top of page 76.

 

[Sam'l B]

Nope -- P. 76 has a discussion of gsub, in the context of "Backslash
Sequences in the Substitution"

 

[dblack]

Hi --

Nope -- P. 76 has a discussion of gsub, in the context of "Backslash
Sequences in the Substitution"

Look in the middle of page 22.


David

--
Q. What's a good holiday present for the serious Rails developer?
A. RUBY FOR RAILS by David A. Black (http://www.manning.com/black)
aka The Ruby book for Rails developers!
Q. Where can I get Ruby/Rails on-site training, consulting, coaching?
A. Ruby Power and Light, LLC (http://www.rubypal.com)

 

[Jeremy McAnally]

That is a parameter passed to a block. It allows the method that
yielded to the block to pass information into the block, which in this
case is a song title (I'm guessing?).

Think of it (sort of) as the method yielding to the block feeding it a
parameter like you would a method call: a value is passed in from the
caller and stored in a local instance to be used in the block.

--Jeremy

 

[Giles Bowkett]

The online version of the first edition of Pickaxe has it here:

http://www.rubycentral.com/book/intro.html

Scroll down to "Blocks and Iterators." It's about 2/3rds down the page.

 

[Devin Mullins]

The online version of the first edition of Pickaxe has it here:

http://www.rubycentral.com/book/intro.html

Scroll down to "Blocks and Iterators." It's about 2/3rds down the page.

Here's an URL with an anchor link, for the especially lazy:
http://phrogz.net/ProgrammingRuby/language.html#blocksclosuresandprocobjects

Note the mention of the rules of parallel assignment, and click the
link. You'll get more info than you ever wanted to know.

Or, at least, *should* have wanted to know. With irb and Test::Unit, who
needs to remember these details?

Devin

 

[Sam'l B]

Hi --



Look in the middle of page 22.


David

Got it! Thanks!

 

[Sam'l B]

That is a parameter passed to a block. It allows the method that
yielded to the block to pass information into the block, which in this
case is a song title (I'm guessing?).

Think of it (sort of) as the method yielding to the block feeding it a
parameter like you would a method call: a value is passed in from the
caller and stored in a local instance to be used in the block.

That's what I had figured out intuitively -- it catches whatever the
method on the left spits out.

Sam'l

 

[Sam'l B]

Here's an URL with an anchor link, for the especially lazy:
http://phrogz.net/ProgrammingRuby/language.html#blocksclosuresandprocobjects


Note the mention of the rules of parallel assignment, and click the
link. You'll get more info than you ever wanted to know.

Or, at least, *should* have wanted to know. With irb and Test::Unit, who
needs to remember these details?

Documentation Nazis and other excessively literal folk,

Sam'l B.

 

[rwtnorton]

Pickaxe Book (2nd Ed.), P. 49, 2nd example, line 3:

@songs.find {|song| title == song.name }

I can't find a definition of the "|song|" construction in the book.
It is intuitively obvious that it is a variable, and a sort of
"catcher's mitt" for the output of the method "@songs.find" -- and
acts that way for all other example in the book that I can find.

What I _can't_ find, though, is a discussion of the construction --
or did I miss it somewhere?

Sam Bassett

Why, it's a chute, of course:
http://poignantguide.net/ruby/chapter-3.html (Section: Block
Arguments)

;-)

(Definitely, my all-time favorite intro-to-a-programming-language text.)

Richard W. Norton