"is_a?" real mystery + more on arrays

[Aran]

Okay, I read on ruby-language (the site :P) that is_a? returns an array, but I don't understand. And second, how do you add to an empty array? third when you use is_a? does that object go to the end of the array?

 

[Daniel]

1. "is_a?" checks if the word before it is equal to the word in parenthesis. The following example would check
if "$scene" is equal to "Scene_Title".

Example:

if $scene.is_a?(Scene_Title)
  # code
end

2. There are two ways. This example adds to the end of the array:

array.push(object)

And this example adds the object to the array's index specified:

array[0] = object

3. I don't think you understand what "is_a?" does.

 

[Aran]

Okay, thanx alot for the first two. And for the third, i guess not, huh? (well i do now XP)

 

[SephirothSpawn]

.is_a? Returns true of false when comparing an objects class

def is_a?(class)
  return self.class == class
end

The actuall mathod probably looks similar to that. it simply checks to see if an objects class is whatever.

So I really have no idea what you are talking about with arrays...

 

[Aran]

oh... then n/m about the arrays and all that ^^. wow, i love u guys.

 

[linkz0r]

Trickster explained well how the is_a? works. But THIS is the default, it isn´t supposed to return arrays. Maybe you misread that or the method was altered by the writer! xD

About Array, daniel explained well too, i just have to add something...

unshift
Adds the given element(s) to the beginning of the array.

a = []    => []
a.unshift "a"    => ["a"]
a.unshift "b", "c", "d"    => ["b", "c", "d", "a"]

insert
Inserts the given element(s) in the given position.

a = []    => []
a.insert 1, "a"    => [nil, "a"]
a.insert 0, "b", "c", "d"    => ["b", "c", "d", nil, "a"]

Please correct me if i´m wrong, i´m in a hurry now ^^

 

[Aran]

thanx alot, LT! Hey, do you have a syntax manual or something?

 

[Mr.Mo]

thanx alot, LT! Hey, do you have a syntax manual or something?

he used the RMXP help file if I'm not mistaken. You should check it because it helps alot. I use it as a reference all the time.

 

[Aran]

Oh... i guess... guess i'll take a look...

 

[rey meustrus]

I use the help file a lot myself too :P I'm finding it helps less over time though...and it would have solved this question. Sometimes we forget that the help file has been translated, and that it pertains to scripting RGSS.

.is_a? Returns true of false when comparing an objects class

def is_a?(class)
  return self.class == class
end

The actuall mathod probably looks similar to that. it simply checks to see if an objects class is whatever.

So I really have no idea what you are talking about with arrays...

If it were that simple, is_a? probably wouldn't exist. It's a definition buried deep within class Object that is probably not defined in Ruby, but in the mother language used to interpret it. It looks to see the signature of the object in memory (inaccessible by ordinary RGSS means) and compares it to the defined class in question.

 

[Prexus]

Aran.. I know you've been learning to script for a long time.. I guess I always just assumed you knew about the Ruby Pragmatic Programming Guide:
http://www.rubycentral.com/book/

Check this for a list of the built-in methods and any syntax as well as a brief explanation with examples of how they work:
http://www.rubycentral.com/book/builtins.html

 

[Aran]

O.O th-thanx s-so much, Prexus... *drool*

 

[syvkal]

I'm not uber amazing at scripting, but just thought I'd say a really useful use for is_a?
You can use it to check if a message is being displayed

$window.is_a?(Window_Message)

And then do coding if it's not
eg. only refresh bars when there's no dialogue (reduces lag i think) and when I made a game where one level the map changes season every now and again I had to update scene_map so the events change so I check if a message was displaying so I didn't get rid of it.

 

[rey meustrus]

There is also a Game_Temp value that controls whether a message is being displayed, it would work better to use that since initialization and dispoing of $window might not be consistent.

 

[syvkal]

Didn't know that :D
Didn't really look...