`self.attribute` calls the method `attribute`.  
`self.attribute = value` calls the method `attribute=` with the argument `value`.  
`@attribute` and `@attribute = value` get/set the value of the instance variable `@attribute`.

So basically they&#39;re two entirely different things.

However if you call `attr_accessor :attribute` it defines the method `attribute` to return `@attribute` and the method `attribute=(value)` to set `@attribute = value`. So in that case, there is no difference.

&quot;Accessing instance variable directly is about two times faster than accessing them with accessor methods&quot;

Check out the: https://www.greyblake.com/blog/2012-09-01-ruby-perfomance-tricks/

How can I convert a symbol type into a string in Emacs lisp? 

I wasn&#39;t able to find a `symbol-to-string` function or anything similar.

Convert Symbol to a String in Elisp

This is because I&#39;d like to automatically run tests after each file save.

I have looked at `autocmd` and `BufWritePost` but cannot make it work.


How to automatically execute a shell command after saving a file in Vim?

Can anyone explain the difference between accessing an instance attribute via `self.attribute` and by `@attribute`?


Directly accessing an instance variable vs. Using an accessor method

<p>Can anyone explain the difference between accessing an instance attribute via <code>self.attribute</code> and by <code>@attribute</code>?</p>


Forgive the beginner question, but say I have an array:

    a = [1,2,3]

And a function somewhere; let&#39;s say it&#39;s an instance function:

    class Ilike
      def turtles(*args)
        puts args.inspect
      end
    end

How do I invoke `Ilike.turtles` with `a` as if I were calling `(Ilike.new).turtles(1,2,3)`.

I&#39;m familiar with `send`, but this doesn&#39;t seem to translate an array into an argument list.

A parallel of what I&#39;m looking for is the Javascript `apply`, which is equivalent to `call` but converts the array into an argument list.

Given an array of arguments, how do I send those arguments to a particular function in Ruby?

I understand the concept of `some_instance.send` but I&#39;m trying to figure out why you can call this both ways. The Ruby Koans imply that there is some reason beyond providing lots of different ways to do the same thing. Here are the two examples of usage:

    class Foo
      def bar?
        true
      end
    end

    foo = Foo.new
    foo.send(:bar?)
    foo.__send__(:bar?)

Anyone have any idea about this?

Ruby send vs __send__

While learning Ruby I&#39;ve come across the &quot;=&gt;&quot; operator on occasion. Usually I see it in the form of 

    :symbol =&gt; value

and it *seems* to be used frequently when passing values to functions. What exactly is that operator called? What does it do/mean? Is it built into Ruby or is it something that different frameworks like Rails and DataMapper add to the symbol class? Is it only used in conjunction with the symbol class? Thanks.

In Ruby what does &quot;=&gt;&quot; mean and how does it work?

I was testing some DB entries in our production server in Rails Console where almost all the commands were producing a huge number of lines of output and causing the ssh channel to hang.

Is there a way to suppress the console/irb screenfuls?

How to suppress Rails console/irb outputs

I am working through Ruby Koans. 

The `test_the_shovel_operator_modifies_the_original_string` Koan in **about_strings.rb** includes the following comment:

&gt; Ruby programmers tend to favor the shovel operator (&lt;&lt;) over the plus
&gt; equals operator (+=) when building up strings.  Why?

My guess is it involves speed, but I don&#39;t understand the action under the hood that would cause the shovel operator to be faster. 

Would someone be able to please explain the details behind this preference?

Why is the shovel operator (&lt;&lt;) preferred over plus-equals (+=) when building a string in Ruby?

Does somebody know how to make private, non-static members in CoffeeScript? Currently I&#39;m doing this, which just uses a public variable starting with an underscore to clarify that it shouldn&#39;t be used outside of the class:

    class Thing extends EventEmitter
      constructor: (@_name) -&gt;

      getName: -&gt; @_name

Putting the variable in the class makes it a static member, but how can I make it non-static? Is it even possible without getting &quot;fancy&quot;?

Private members in CoffeeScript?

Let&#39;s say I have a `Gift` object with `@name = &quot;book&quot;` &amp; `@price = 15.95`. What&#39;s the best way to convert that to the Hash `{name: &quot;book&quot;, price: 15.95}` in Ruby, not Rails (although feel free to give the Rails answer too)?

Ruby convert Object to Hash

I see it recommended all over the place when coding for iOS that properties should be used for accessing instance variables because of the benefits this lends to memory management, among other things.

This advice doesn&#39;t sit terribly well with me. I find that using properties instead of plain old ivars just takes too much code and I don&#39;t really see the benefits if you&#39;re comfortable with memory management. Is it really that important? What&#39;s your approach to managing instance variables?

Must every ivar be a property?

What are Ruby variables preceded with double at signs (`@@`)? My understanding of a variable preceded with an at sign is that it is an instance variable, like this in PHP:

PHP version

    class Person {
    
        public $name;

        public function setName($name) {
            $this-&gt;name = $name;
        }
    
        public function getName() {
            return $this-&gt;name;
        }
    }

Ruby equivalent

    class Person

        def set_name(name)
            @name = name
        end

        def get_name()
            @name
        end
    end

What does the double at sign `@@` mean, and how does it differ from a single at sign?

What does @@variable mean in Ruby?

Let&#39;s say I have the following hash:

    { :foo =&gt; &#39;bar&#39;, :baz =&gt; &#39;qux&#39; }

How could I dynamically set the keys and values to become instance variables in an object...

    class Example
      def initialize( hash )
        ... magic happens here...
      end
    end

... so that I end up with the following inside the model...

    @foo = &#39;bar&#39;
    @baz = &#39;qux&#39;


?
      

Ruby Metaprogramming: dynamic instance variable names

I was just curious about this: the following code will not compile, because we cannot modify a foreach iteration variable:


            foreach (var item in MyObjectList)
            {
                item = Value;
            }

But the following will compile and run:

            foreach (var item in MyObjectList)
            {
                item.Value = Value;
            }

Why is the first invalid, whereas the second can do the same underneath (I was searching for the correct english expression for this, but I don&#39;t remember it. Under the...? ^^ )

Why can&#39;t we assign a foreach iteration variable, whereas we can completely modify it with an accessor?

I learned c# recently, so when I learned to write properties, I was taught to do it like this:

    public string Name { get; set; }

Auto properties are great! But now I&#39;m trying to do something a little more complicated, so I need to write a custom pair of accessors.

    private string _Name;
    public string Name {
        get { return _Name; }
        set { _Name = value }
    }

I know the compiler makes a private instance variable down in it&#39;s murky depths when one uses autos, but I&#39;m spoiled and don&#39;t want that private variable sitting around looking pointless.

Is there a way to use custom accessors without a private variable?

C# Custom getter/setter without private variable

At the moment, `TypeScript` does not allow use get/set methods(accessors) in interfaces.
For example:

    interface I {
          get name():string;
    }

    class C implements I {
          get name():string {
              return null;
          } 
    }

	
furthermore, TypeScript does not allow use Array Function Expression in class methods:
for ex.:

    class C {
        private _name:string;
    
        get name():string =&gt; this._name;
    }

Is there any other way I can use a getter and setter on an interface definition?


Is it possible to use getters/setters in interface definition?

I&#39;m learning Swift and I&#39;m reading *The Swift Programming Language* from Apple. I don&#39;t have any Objective-C background (only [PHP][1], JavaScript, and others, but not Objective-C).

On page 24-25 I see this code:

    //...Class definition stuff...

    var perimeter: Double {
        get {
            return 3.0 * sideLength
        }
        set {
            sideLength = newValue / 3.0
        }
    }

    //...Class continues...

This part is *not* specified in the book, and I can&#39;t get what those are for.

What are **get** and **set**?

  [1]: https://en.wikipedia.org/wiki/PHP



What are &#39;get&#39; and &#39;set&#39; in Swift?

Is there a way to have a private setter for a property in TypeScript?

	class Test
	{
		private _prop: string;
		public get prop() : string
		{
			return this._prop;
		}

		private set prop(val: string)
		{
			//can put breakpoints here
			this._prop = val;
		}
	}

Compiler complains that visibility for getter and setter don&#39;t match. I know I can just set the backing field, but but then I can&#39;t set breakpoints when the value is set.

I though about using an interface to hide the setter, but interfaces can only define a property, not whether it has a getter on setter.

Am I missing something here? There doesn&#39;t seem to be any reason to not allow private setters, the resulting JS doesn&#39;t enforce visibility anyway, and seems better that the current alternatives.

Am I missing something? If not is there a good reason for no private setters?

Content Type	Original Author	Original Content on Stackoverflow
Question	pistacchio	View Question on Stackoverflow
Solution 1 - Ruby	sepp2k	View Answer on Stackoverflow
Solution 2 - Ruby	meso_2600	View Answer on Stackoverflow

Directly accessing an instance variable vs. Using an accessor method

Ruby Problem Overview

Ruby Solutions

Solution 1 - Ruby

Solution 2 - Ruby

How to automatically execute a shell command after saving a file in Vim?

Convert Symbol to a String in Elisp

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