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Hello and welcome to this lecture.

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In this lecture or Our be talking to you about variable scope in Ruby.

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What is a variable scope is scope basically describes the areas within a program where the variable

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is assessable from.

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There are several types of scopes available within Ruby.

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We've caught what is known as a local variable.

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You can usually tell the scope of a variable by their name.

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So with a local school the name is usually in law case or in lower case.

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But on score as well see you have to depend on the name have a variable that's called an amount on the

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score order.

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You can tell if you see a lower case you can tell that is the local variable or if it is just a variable

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chord amount or order.

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You can also tell as long as it's in lower case and it contains a character A to Z or an score.

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You can identify that as the local variable local variable available in a local scope.

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A little cool variable or lack of variables are local to the code construct in which they are declared.

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For example if you have a function and you declare a variable within that function that variable is

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only accessible from within that function.

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That will be the scope.

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We've also got a global scope of global variable and you can identify that here.

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The name of the variable has got a dollar sign in front of it.

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So global variables in Ruby are sensible from anywhere in the Ruby program.

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This is regardless of where they are hard to click so it doesn't matter where you declare the variable

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it is global.

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It is a sensible anywhere within the Ruby program.

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There are advantages disadvantage Surrey The Disadvantages of an arsehole is not encouraged.

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Not a lot of people in quarries using global variables.

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The reason being is that when you use global variables they are visible anywhere in the code or hip

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program.

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The code record for your program anywhere within that code you can see the global variables and they

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can also be changed from anywhere within the application.

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So this makes it very difficult to track any bug changes or any issues with the code makes it very difficult

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to track the global variable.

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If the scope is global.

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Next we've got the instance variables.

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You can identify that with the dollar sign then names usually have just at the last I'm sorry go.

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The at symbol in front of the name.

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So whereby you see the at symbol in front of a name it's an instance variable what is available within

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the instance.

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So basically an instance the values are local to specific instances of an object.

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Okay so a b will only be available within a specific instance of an object.

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Next we've also got what is known as a class scope.

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You can identify the variables in a class score because you've got double at symbol a class called classes

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in Ruby B's clean and first class objects so each class is an instance of a class of the ruby class.

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If you know what I mean.

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So with new classes created an object of the type class is in initialize had assigned a global constant

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So when you create the class you are beat you don't expect the name of the class to change.

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It becomes constant.

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Then body it will have other things within that class.

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But you can instantiate.

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You can create an instance of that class or the instances of that class or objects that belong to that

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class.

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All share the same variable scope.

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So a class variable is a variable that is shared among all the instances of a class with also got what

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is called a constant.

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Then you can identify a constant.

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By the way they are named.

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So with a constant you usually have it in capital capitals.

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Or the first letter is usually capital.

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You can identified because of capitals so Ruby constants are values which are which ones you've assigned

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the values are not meant to be changed.

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However Ruby does let you change them but it will warn you before you change them in all other programming

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languages.

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It doesn't you may not be able to do that once you've given it a value.

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But Ruby does let you change it but give me a warning before it does.

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Ruby also have what we called pseudo variables so this the variable variables which can not be assigned

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values you can't give them values.

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Example include Neil.

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Neil basically is is a sign to initialize a variable so when you create a variable you don't give it

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a value is referred to as nil.

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Also you've got self serve basically refers to the currently executing object.

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You can usually detect the scope of a variable by their names but you can also programmatically detect

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what scope a variable in.

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So what do we do that there is a method you can use.

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So let's say I created a variable and then give you the value of 7.

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Okay so we know that variable is 7.

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So if I want to find out what scope that variable it's in.

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Already know it's a local variable because it's in lower case.

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Well I can also find that out by type name the method defined.

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Followed by a question mark.

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Space and then a variable name and press centre.

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You can see it told me that is a local variable.

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So if I did the same thing I created say I have a dollar sign X and said that two equals to seven.

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If I come here and do find.

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Question mark.

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And then Darla X here to me this gorp is global.

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So you know you get the idea.

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So you can do the same once you know the symbol of how to identify.

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You can usually identify by the by the symbols in front of variable names.

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So you know that you can use that to identify or you can do programmatically I have done here.

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So that's basically it.

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How about variable scopes in Ruby.

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Thanks for watching.

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I hope it has made sense if it hasn't.

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Please let me know.

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I'll be more than happy to explain further.

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Thanks for watching.

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Thanks for your time.

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Bye.