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Newbie trying to understand object oriented programming

Started bybit-naughty@hotmail.com
First post2016-02-05 06:55 -0800
Last post2016-02-06 11:56 -0200
Articles 6 on this page of 46 — 14 participants

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  Newbie trying to understand object oriented programming bit-naughty@hotmail.com - 2016-02-05 06:55 -0800
    Re: Newbie trying to understand object oriented programming 4ndre4 <4ndre4@4ndre4.com.invalid> - 2016-02-05 18:56 +0000
    Re: Newbie trying to understand object oriented programming Tim Slattery <tim@risingdove.com> - 2016-02-05 14:07 -0500
    Re: Newbie trying to understand object oriented programming Aleksandro <aleksandro@gmx.com> - 2016-02-05 17:34 -0300
      Re: Newbie trying to understand object oriented programming Scott Sauyet <scott.sauyet@gmail.com> - 2016-02-05 19:10 -0800
        Re: Newbie trying to understand object oriented programming 4ndre4 <4ndre4@4ndre4.com.invalid> - 2016-02-06 08:33 +0000
          Re: Newbie trying to understand object oriented programming Scott Sauyet <scott.sauyet@gmail.com> - 2016-02-06 08:24 -0800
            Re: Newbie trying to understand object oriented programming 4ndre4 <4ndre4@4ndre4.com.invalid> - 2016-02-06 18:48 +0000
              Re: Newbie trying to understand object oriented programming Scott Sauyet <scott.sauyet@gmail.com> - 2016-02-06 12:28 -0800
                Re: Newbie trying to understand object oriented programming 4ndre4 <4ndre4@4ndre4.com.invalid> - 2016-02-06 21:01 +0000
                  Re: Newbie trying to understand object oriented programming Scott Sauyet <scott.sauyet@gmail.com> - 2016-02-07 15:23 -0800
                    Re: Newbie trying to understand object oriented programming Aleksandro <aleksandro@gmx.com> - 2016-02-08 11:45 -0300
              Re: Newbie trying to understand object oriented programming "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2016-02-08 13:39 -0800
                Re: Newbie trying to understand object oriented programming Scott Sauyet <scott.sauyet@gmail.com> - 2016-02-11 08:09 -0800
                  Re: Newbie trying to understand object oriented programming "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2016-02-11 12:22 -0800
                    Re: Newbie trying to understand object oriented programming John Harris <niam@jghnorth.org.uk.invalid> - 2016-02-12 11:09 +0000
                      Re: Newbie trying to understand object oriented programming "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2016-02-12 13:34 -0800
                        Re: Newbie trying to understand object oriented programming John Harris <niam@jghnorth.org.uk.invalid> - 2016-02-13 14:40 +0000
                          Re: Newbie trying to understand object oriented programming "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2016-02-14 10:18 -0800
                            Re: Newbie trying to understand object oriented programming Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-02-14 21:27 +0100
                            Re: Newbie trying to understand object oriented programming "J. Clarke" <j.clarke.873638@gmail.com> - 2016-05-14 10:13 -0400
                              Re: Newbie trying to understand object oriented programming Tim Streater <timstreater@greenbee.net> - 2016-05-14 16:47 +0100
                                Re: Newbie trying to understand object oriented programming "J. Clarke" <j.clarke.873638@gmail.com> - 2016-05-15 07:05 -0400
                              Re: Newbie trying to understand object oriented programming "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2016-05-14 10:08 -0700
                                Re: Newbie trying to understand object oriented programming "J. Clarke" <j.clarke.873638@gmail.com> - 2016-05-15 07:02 -0400
                                  Re: Newbie trying to understand object oriented programming "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2016-05-15 13:11 -0700
                              Re: Newbie trying to understand object oriented programming John Harris <niam@jghnorth.org.uk.invalid> - 2016-05-15 17:03 +0100
                                Re: Newbie trying to understand object oriented programming "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2016-05-15 13:20 -0700
                                Re: Newbie trying to understand object oriented programming Gene Wirchenko <genew@telus.net> - 2016-05-16 11:55 -0700
                            Re: Newbie trying to understand object oriented programming Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-05-16 21:39 +0200
                              Re: Newbie trying to understand object oriented programming "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2016-05-17 07:30 -0700
                              Re: Newbie trying to understand object oriented programming John Harris <niam@jghnorth.org.uk.invalid> - 2016-05-17 15:34 +0100
                        Re: Newbie trying to understand object oriented programming Scott Sauyet <scott.sauyet@gmail.com> - 2016-02-13 17:50 -0800
                          Re: Newbie trying to understand object oriented programming John Harris <niam@jghnorth.org.uk.invalid> - 2016-02-14 11:15 +0000
                          Re: Newbie trying to understand object oriented programming "Michael Haufe (TNO)" <tno@thenewobjective.com> - 2016-02-14 11:03 -0800
                            Re: Newbie trying to understand object oriented programming John Harris <niam@jghnorth.org.uk.invalid> - 2016-02-15 20:18 +0000
                    Re: Newbie trying to understand object oriented programming Scott Sauyet <scott.sauyet@gmail.com> - 2016-02-13 16:54 -0800
    Re: Newbie trying to understand object oriented programming Danny <dann90038@gmail.com> - 2016-02-05 15:00 -0800
    Re: Newbie trying to understand object oriented programming RobG <rgqld@iinet.net.au> - 2016-02-06 17:18 +1000
      Re: Newbie trying to understand object oriented programming Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2016-02-06 16:01 +0100
      Re: Newbie trying to understand object oriented programming bit-naughty@hotmail.com - 2016-02-07 04:47 -0800
        Re: Newbie trying to understand object oriented programming Tim Streater <timstreater@greenbee.net> - 2016-02-07 13:16 +0000
        Re: Newbie trying to understand object oriented programming John Harris <niam@jghnorth.org.uk.invalid> - 2016-02-07 17:29 +0000
          Re: Newbie trying to understand object oriented programming bit-naughty@hotmail.com - 2016-02-08 08:53 -0800
            Re: Newbie trying to understand object oriented programming Tim Streater <timstreater@greenbee.net> - 2016-02-08 17:33 +0000
    Re: Newbie trying to understand object oriented programming Joao Rodrigues <jr@none.com> - 2016-02-06 11:56 -0200

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#29573

Frombit-naughty@hotmail.com
Date2016-02-07 04:47 -0800
Message-ID<9ffad5b6-4de6-463c-b919-bd139402c94e@googlegroups.com>
In reply to#29556
On Saturday, February 6, 2016 at 12:49:07 PM UTC+5:30, RobG wrote:

> So *this* references an 
> object that is a new instance of *vegetables*.
> 


Ahh - THIS was the sentence that taught me the most out of everything you guys said.
OK, well, this is going to take some time to sink into my brain, I'm just going to have to sleep on it till I get it.

WHY have they done all this? Like, why have things been laid out this way? The idea behind OOP is that - MANY programmers will be collaborating on ONE piece of software, right? Like "Vegetables" will be written by somebody else, and I'll just be instantiating it, and using its insides in my code, without caring about what it's inside it, right? First of all, how do I know that it'll be called "Vegetables" - do I have to chat with the guy who wrote it and ask him/her what he/she called it inside his/her code???!!!
Is an easy way to learn this stuff to use *libraries*, where I will, have to call, code that someone else wrote, I mean, that's the whole point of  a library, of course.....

I find the statement "this.colour=colour" inside the function that someone said very confusing, can we just name the variables separately, like "this.hue=colour", it's still the same thing, "potatoes.hue" will then be "brown",right? How do I then get "tomatoes.hue" to be "red"?


I know that you can get fat books on OOP, will I have to read those to understand all the answers to my questions? I hope not! :) (I even tried reading one once, didn't understand a word, it just put me to sleep! :) )
I DO intend to stick with Javscript, yes, mainly cause that's the only language available inside a browser, and I want to make websites (which ignores anything of what the language IS, of course - but I'm helpless :( ).

Thanks to all you guys though :)

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#29574

FromTim Streater <timstreater@greenbee.net>
Date2016-02-07 13:16 +0000
Message-ID<070220161316290875%timstreater@greenbee.net>
In reply to#29573
In article <9ffad5b6-4de6-463c-b919-bd139402c94e@googlegroups.com>,
<bit-naughty@hotmail.com> wrote:

>On Saturday, February 6, 2016 at 12:49:07 PM UTC+5:30, RobG wrote:
>
>> So *this* references an 
>> object that is a new instance of *vegetables*.
>> 
>
>
>Ahh - THIS was the sentence that taught me the most out of everything you guys
>said.
>OK, well, this is going to take some time to sink into my brain, I'm just
>going to have to sleep on it till I get it.
>
>WHY have they done all this? Like, why have things been laid out this way? The
>idea behind OOP is that - MANY programmers will be collaborating on ONE piece
>of software, right? Like "Vegetables" will be written by somebody else, and
>I'll just be instantiating it, and using its insides in my code, without
>caring about what it's inside it, right? First of all, how do I know that
>it'll be called "Vegetables" - do I have to chat with the guy who wrote it and
>ask him/her what he/she called it inside his/her code???!!!
>Is an easy way to learn this stuff to use *libraries*, where I will, have to
>call, code that someone else wrote, I mean, that's the whole point of  a
>library, of course.....
>
>I find the statement "this.colour=colour" inside the function that someone
>said very confusing, can we just name the variables separately, like
>"this.hue=colour", it's still the same thing, "potatoes.hue" will then be
>"brown",right? How do I then get "tomatoes.hue" to be "red"?

It will be brown only because you insisted on putting:

  this.colour = "brown"

inside your object constructor. You should have put:

  spuddy = new vegetable ("brown")

and for the constructor you have:

  function vegetable (colour)
  this.hue = colour

then you'll be doing:

  tomahto = new vegetable ("red")


I though this had already been pointed out?

-- 
"Please stop telling us what you feel. Please stop telling us what your 
intuition is. Your intuitive feelings are of no interest whatsoever, 
and nor are mine. I don't give a bugger what you feel, or what I feel. 
I want to know what the evidence shows."             -- Richard Dawkins

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#29576

FromJohn Harris <niam@jghnorth.org.uk.invalid>
Date2016-02-07 17:29 +0000
Message-ID<djvebb1m6snmue6vo58jqu9r7o3rihq93k@4ax.com>
In reply to#29573
On Sun, 7 Feb 2016 04:47:25 -0800 (PST), bit-naughty@hotmail.com
wrote:

  <snip>
>WHY have they done all this? Like, why have things been laid out this way? 
  <snip>

What follows might help you. It says where it all comes from.


Question : What is an object? That's "object" as in "Object
Oriented." Answer : An object is something that can jump up and down
and scream and shout and hurl rocks. Better still, it's something
that knows how to do those things without your help. If you want it
to hurl a rock you just say "hurl!" and it does that.

Of course, we are talking about software here so instead of saying
"hurl!" we call the objects's "hurl" function. You can think of this
function being inside the object if you wish. But suppose you have
two rock-hurling objects : one at the front of your castle, the
other at the back. Call them f and b. If f and b have separate
copies of the function's code inside themselves then it's not nice.
If you have thousands of rock-hurling objects it becomes very
inefficient. This problem is solved by having one copy of the
function that is shared by all the rock-hurling objects. The one
copy is kept somewhere known to rock-hurling objects. The function
belongs to them.

To hurl a rock you need to say which rock-hurler should hurl and
call its hurl function. In ECMAScript, and several other languages,
to make object b hurl you do  b.hurl();  (assume there are no
parameters needed here).

Now the hurl function is shared by all rock-hurling objects but it
will probably need to access something inside the object. How does
it know that it is object b? That's what "this" does. The compiler
arranges for "this" to be the same object as b. If the hurl
function needs to increment b's count property its code does
  this.count += 1;  and so on.

These rock-hurling objects must have come into existence somehow.
The usual way is for somewhere in the program to do
  f = new RockHurler(); b = new RockHurler();
RockHurler is a constructor function. That is, its job is to help
build a new object of a particular kind, a rock-hurler in this
example.

A constructor usually needs to give the new object properties with
suitable values. As before, the compiler arranges for "this" to be
the object that the function is to work on. Expect the code in the
constructor to do  this.count = 0;  among other things.


What has been said so far applies as much to C++ and Java as it
does to ECMAScript. There are details that have not been discussed.
This is where there tend to be differences between languages,
especially in ECMAScript.


  John

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#29580

Frombit-naughty@hotmail.com
Date2016-02-08 08:53 -0800
Message-ID<a297cc47-5163-4ca7-b0f3-a1174cc72348@googlegroups.com>
In reply to#29576
On Sunday, February 7, 2016 at 10:59:23 PM UTC+5:30, John Harris wrote:

> Now the hurl function is shared by all rock-hurling objects 

AHH - THIS was the vital info that was of most importance in everything you said.

Wow! Thanks for typing all that out, man, appreciate it :)

But the question is, when writing a piece of software, how do you predict that there's *going to _be_ a lot of rock-hurling objects, all of whom will *need* to have the same "hurl" function inside them* ? 
How often does this actually occur?

Could someone please also answer the stuff I asked above about "Vegetables", as in, multiple people working on the same code?

...and also the stuff about libraries?


Thanks.

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#29581

FromTim Streater <timstreater@greenbee.net>
Date2016-02-08 17:33 +0000
Message-ID<080220161733161611%timstreater@greenbee.net>
In reply to#29580
In article <a297cc47-5163-4ca7-b0f3-a1174cc72348@googlegroups.com>,
<bit-naughty@hotmail.com> wrote:

>On Sunday, February 7, 2016 at 10:59:23 PM UTC+5:30, John Harris wrote:
>
>> Now the hurl function is shared by all rock-hurling objects 
>
>AHH - THIS was the vital info that was of most importance in everything you
>said.
>
>Wow! Thanks for typing all that out, man, appreciate it :)
>
>But the question is, when writing a piece of software, how do you predict that
>there's *going to _be_ a lot of rock-hurling objects, all of whom will *need*
>to have the same "hurl" function inside them* ? 

Well that'll be a matter for you. It'll show up in your design that
this object and that one need the same *hurl* function. If OTOH the
*hurl* function is different, you'll need another class. Note that you
can still call it *hurl* in both classes if you want, if it's doing
essentially the same thing but requires different code in the two
cases.

>How often does this actually occur?

Any time you've got lots of the same object showing up in your app.
Rows in a table, f'rinstance, are likely to be all the same. Or tables,
if you've got a number of those.

-- 
Anyone who slaps a 'this page is best viewed with Browser X' label on
a Web page appears to be yearning for the bad old days, before the Web,
when you had very little chance of reading a document written on another
computer, another word processor, or another network. -- Tim Berners-Lee

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#29561

FromJoao Rodrigues <jr@none.com>
Date2016-02-06 11:56 -0200
Message-ID<n94u26$5pp$1@gioia.aioe.org>
In reply to#29543
bit-naughty@hotmail.com wrote:
> Hi, OK, I've read about and tried to understand OOP for a long time
> now, but I don't think I really get it.

In this case, I'd suggest reading this article in MDN:
<https://developer.mozilla.org/en-US/docs/Web/JavaScript/Introduction_to_Object-Oriented_JavaScript>


> This question just popped
> into my head while mulling the whole thing over:
>
> "this" means *that one*, right? Like, it's a cookie cutter.....?
>
> Then what about this?:
>
> if I have:
>
> function vegetables() { this.colour="brown"; }

There is a convention about constructor functions that their names 
should start with an upper case letter. Then you should write:

function Vegetables() {
   this.colour = "brown";
}

>
> and I do both a var potatoes = new vegetables() ;
>
> AND a var tomatoes = new vegetables();
>
>
> Then BOTH potatoes.colour will be "brown" *AND* tomatoes.colour will
> be "brown", right.....??!!!

Yes, because all instances of Vegetables will have the property 'colour' 
with the same value ('brown').

You should have declared Vegetables() as:

function Vegetables(colour) {
   this.colour = colour;
}

var tomato = new Vegetables('red');
console.log(tomato.colour); // red

var potato = new Vegetables('brown');
console.log(potato.colour); // brown

Douglas Crockford once wrote: "JavaScript is a prototypal language, but 
it has a *new* operator that tries to make it look sort of like a 
classical language. That tends to confuse programmers, leading to some 
problematic programming patterns."
<http://yuiblog.com/blog/2006/11/13/javascript-we-hardly-new-ya/>

It would be simpler if you used:

var vegetables = {
   tomatoes: {
     colour: 'red'
   },
   potatoes: {
     colour: 'brown'
   }
};

It is even simpler if you need to add properties to vegetables:

vegetables.bananas = {colour: 'yellow'};

var tomato = vegetables.tomatoes;
console.log(tomato.colour); // red

var potato = vegetables.potatoes;
console.log(potato.colour); // brown

var banana = vegetables.bananas;
console.log(banana.colour); //yellow


ECMAScript 2015 (aka ES6) introduced "class", which is a syntactical 
sugar over JavaScript's existing prototype-based inheritance. See:
<https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Classes>

class Vegetables {
   constructor(colour) {
     this.colour = colour;
   }
}

var potatoes = new Vegetables('brown');
console.log(potatoes.colour); // brown


--
Joao Rodrigues

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