## Where did this value variable come from?

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I was reading through an example of how to use metaprogramming to make attribute accessors, and I'm a bit confused on where this value variable came from:

```class AttrAccessorObject
def self.my_attr_accessor(*names)
names.each do | name |
define_method(name) {
self.instance_variable_get("@#{name}".to_sym)
}
define_method("#{name}=") do | value |
self.instance_variable_set("@#{name}".to_sym, value)
end
end
end
end
```

I understand that the instance_variable_set method needs both the instance variable and the value to set the instance variable's new value, but where did this value variable in the code come from? Also, since it's using a "do/end" loop to use the value, I'm assuming that the "define_method("#{name}=") evaluates to an array of values, is that correct?

If you think of what a 'normal' method definition looks like:

```def some_name=(value)
@some_name = value
end
```

The `|value|` part is the same as `(value)` - it declares the arguments that are accepted by the method you're defining. So if I wanted to make a method that takes 3 args:

```define_method(:some_method) do |arg1, arg2, arg2|
[arg1, arg2, arg3]
end
```

Also, since it's using a "do/end" loop to use the value, I'm assuming that the "define_method("#{name}=") evaluates to an array of values, is that correct?

No, blocks are not just used with arrays. Think of a block like an anonymous function that is used as a parameter for another function. The function you call (e.g. `each`) may internally invoke the anonymous function 0, 1, or any number of times. In the case of `each`, it calls it N times (one time for each array element):

```def my_each(array, &blk)
for elem in array do
blk.call(elem)
end
end
```

but in the case of `tap`, it calls it only once:

```def my_tap(obj, &blk)
blk.call(obj)
obj
end
```

Variable (mathematics), In mathematics, a variable is a symbol used to represent an arbitrary element of a set. "Variable" comes from a Latin word, variābilis, with "vari(us)"' meaning Vi�te's convention was to use consonants for known values and vowels for� Almost a century later Leonhard Euler fixed the terminology of infinitesimal calculus and introduced the notation y = f(x) for a function f, its variable x and its value y. Until the end of the 19th century, the word variable referred almost exclusively to the arguments and the values of functions.

`value` is part of method signature you are defining.

`define_method` can be explained as adding a "label" to the block of code and saving it's reference in the class for later consumption.

```define_method("print_two_values") do | value1, value2 |
puts "first: #{value1}, second: #{value2}"
end
```

Can be rewritten as

```def print_two_values(value1, value2)
puts "first: #{value1}, second: #{value2}"
end
```

Variable (computer science), In computer programming, a variable or scalar is a storage location paired with an associated symbolic name, which contains some known or unknown quantity of information referred to as a value. The variable name is the usual way to reference the stored value, in addition Automatic variables: Each local variable in a function comes into existence� Hello, I need help. I want a %let statement to equal a variable's value. If variable order had values of 1-10, I want %let x = order to resolve to the value of order, if the line had 5 for order I want x to be 5, currently for everything I've tried it always resolves to the variable name. Thanks!

It should not go unsaid that there are some weaknesses with the referenced code.

1. There is no need to convert the first argument of Object#instance_variable_get and Object#instance_variable_set to a symbol.

2. (Picky) There is no need for `self.` to precede `instance_variable_get` and `instance_variable_set`, as `self` is the implied receiver when a method is invoked without an explicit receiver.

3. (Mainly) The method is unnecessarily complex as it is much easier to use Ruby's method Module#attr_accessor, which is purpose-built to create getter and setter methods:

```class AttrAccessorObject
def self.my_attr_accessor(*names)
attr_accessor(*names)
end
end
```
```AttrAccessorObject.my_attr_accessor "pig", "owl"
#=> ["pig", "owl"]
AttrAccessorObject.instance_methods(false)
#=> [:pig, :pig=, :owl, :owl=]
inst = AttrAccessorObject.new
#=> #<AttrAccessorObject:0x00005661152d6ed8>
inst.owl = 'hoot'
#=> "hoot"
inst.owl
#=> "hoot"
```

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• `value` is part of the method signature. That mean that defined method will accept one argument. If you use two variables `define_method("#{name}_with_two") do | value1, value2 |` - defined method will accepts two arguments.
• `do ... end` is not a loop. It is a block, which is an ubiquitous concept in Ruby. It is imperative you understand blocks before you can read Ruby. For example, here. Specifically, `define_method` defines a method, and attaches the block as the method's body.
• 4. The method is unnecessarily complex as `Module#attr_accessor` takes a splat parameter for the names: `class AttrAccessorObject; def self.my_attr_accessor(*names) attr_accessor(*names) end end` :-P
• I reckon the goal of their excercise was to recreate `attr_accessor`, so calling the built-in would be missing the point