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gdevelop:tutorials:howtousevariables [2015/05/18 12:28]
127.0.0.1 external edit 		gdevelop:tutorials:howtousevariables [2020/12/26 13:56] (current)
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 Variables are extremely useful in a game: They can be used to remember lots of information, like the life of the player, the state of an object, the amount of ammo available...\\ Variables are extremely useful in a game: They can be used to remember lots of information, like the life of the player, the state of an object, the amount of ammo available...\\
-In this tutorial, we are going to show how to uses variables in different context.+In this tutorial, we are going to show how to uses variables in different contexts.
  
 You can download the small project used for the tutorial here: **[[http://www.compilgames.net/dl/VariablesTutorial.zip]]**\\ You can download the small project used for the tutorial here: **[[http://www.compilgames.net/dl/VariablesTutorial.zip]]**\\
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 And of course, do not hesitate to experiment with the project and the events! :-) And of course, do not hesitate to experiment with the project and the events! :-)
 +
 +**3 Kinds of Variables**
 +  *Global Variables
 +  *Scene Variables
 +  *Object Variables (also called Instance Variables)
 +
 +All of these variables can have default values specified in the editor.
 +
 ===== Quick reminder about variables in GDevelop  ===== ===== Quick reminder about variables in GDevelop  =====
  
-Variables allow you to store data, for example a number or a text. We might compare them to drawers or boxes where we can file notes. Any data can be stored, as long as it is in text or number format: number of lives remaining, high-score, bullets left, killed enemies, etc… You are probably going to use numbers often.+Variables allow you to store data, for example, a number or a text. We might compare them to drawers or boxes where we can file notes. Any data can be stored, as long as it is in text or number format: a number of lives remaining, high-score, bullets left, killed enemies, etc… You are probably going to use numbers often.
  
-Variables are attached to a scene ( We call them **Scene** variable ) or to the game ( **Global** variables ). The values of global variables are not changed when switching to a new scene, whereas scene variables are reset.\\+Variables are attached to a scene ( We call them **Scene** variable ) or to the game ( **Global** variables ). Scene Variables can be viewed by right-clicking the scene editor workspace and selecting properties. Global Variables can be viewed under the Game Settings Tab of the Project Manager. The values of global variables are not changed when switching to a new scene, whereas scene variables are reset.\\
 Every object of a scene can also have its own set of variables: In this case, the variables are called **Object** variables. Every object of a scene can also have its own set of variables: In this case, the variables are called **Object** variables.
  
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 Variables are also often used to store the life/ammo or any other amount related to the player or to objects.\\ Variables are also often used to store the life/ammo or any other amount related to the player or to objects.\\
-In our example, the life is stored inside a scene variable called ''Life''. By default, the variable is set to 100 ( In the project manager, make a right click on the scene and choose 'Initial variables' to show the initial values set. )+In our example, life is stored inside a scene variable called ''Life''. By default, the variable is set to 100 ( In the project manager, make a right-click on the scene and choose 'Initial variables' to show the initial values set. )
  
-When the player click on the character, the character is sent in the air and a hurt animation is set. We also want to decrease the life by 20:+When the player clicks on the character, the character is sent in the air and a hurt animation is set. We also want to decrease life by 20:
  
 {{ gdevelop:tutorials:variablestutorial_2_.png?nolink |}} {{ gdevelop:tutorials:variablestutorial_2_.png?nolink |}}
  
 Here we've just used an action to decrease the variable, so whenever the player is clicked, the life will be decreased.\\ Here we've just used an action to decrease the variable, so whenever the player is clicked, the life will be decreased.\\
-Note that the conditions ensures that the actions won't be repeated more than one time in a row ( Otherwise, it would decrease the life several times per second, and we do not want this! )+Note that the conditions ensure that the actions won't be repeated more than one time in a row ( Otherwise, it would decrease the life several times per second, and we do not want this! )
  
 ==== Progressively increase a variable ==== ==== Progressively increase a variable ====
  
-Sometimes, we want to increase a variable more slowly. It can be done easily using the ''TimeDelta'' function, which returns the time, in seconds, to compute the latest frame displayed.+Sometimes, we want to increase the variable more slowly. It can be done easily using the ''TimeDelta'' function, which returns the time, in seconds, to compute the latest frame displayed.
 Here, we just increase the life of the player at the rate of 5 points per seconds: Here, we just increase the life of the player at the rate of 5 points per seconds:
  
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 {{ gdevelop:tutorials:variablestutorial_5_.png?nolink |}} {{ gdevelop:tutorials:variablestutorial_5_.png?nolink |}}
  
-Note that these kind of events must be done at the end of the event sheet, or at least put after every events modifying the variable, otherwise these events could change again the value of the variable and make it go out of the range.+Note that these kinds of events must be done at the end of the event sheet or at least put after every event modifying the variable, otherwise these events could change again the value of the variable and make it go out of the range.
  
 ==== Displaying a variable on the screen ==== ==== Displaying a variable on the screen ====
  
 Showing the value of a variable to the player is easy: Put a ''Text'' object somewhere on the scene.\\ Showing the value of a variable to the player is easy: Put a ''Text'' object somewhere on the scene.\\
-Then, just add an event setting the text of the object:+Then, just add an event set the text of the object:
  
 {{ gdevelop:tutorials:variablestutorial_6_.png?nolink |}} {{ gdevelop:tutorials:variablestutorial_6_.png?nolink |}}
  
-The value is get using the ''Variable(Life)'' part. Then, we convert it to a text using ''ToString'', and finally, we concatenate it with a small text ( Always remember to use quotes when you want to display a text ).+The value is to get using the ''Variable(Life)'' part. Then, we convert it to a text using ''ToString'', and finally, we concatenate it with a small text ( Always remember to use quotes when you want to display a text ).
 We've also added a call to the ''round'' function so that the variable is displayed as a whole number without decimal places: ''"Life: "+ToString(round(Variable(Life)))''. We've also added a call to the ''round'' function so that the variable is displayed as a whole number without decimal places: ''"Life: "+ToString(round(Variable(Life)))''.
  
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 GDevelop supports an advanced feature for variables called ''Structures''. GDevelop supports an advanced feature for variables called ''Structures''.
-Variables in GDevelop can contains either a number, a text or be a **structure**. In this case, it has no value, but it contains instead other variables, called the **child variables**.\\ +Variables in GDevelop can contain either a number, a text, or be a **structure**. In this case, it has no value, but it contains instead other variables, called the **child variables**.\\ 
-Of course, these child variables can contains numbers, texts or also be structures variables themselves.+Of course, these child variables can contain numbers, texts, or also be structures variables themselves.
  
-If you want to use a variable as a structure, you just have to avoid changing its value or text ( As structures variables do not have any value ). Then, to modify the value of a child variable, just enter as variable name: the **name** of the variable followed by a **period** and finally **the name of the child** variable. For example: ''PlayersStats.NumberOfDeaths''.+If you want to use a variable as a structure, you just have to avoid changing its value or text ( As structure variables do not have any value ). Then, to modify the value of a child variable, just enter as variable name: the **name** of the variable followed by a **period** and finally **the name of the child** variable. For example: ''PlayersStats.NumberOfDeaths''.
  
-As normal variables, if the child does not exists, it will be created.\\+As normal variables, if the child does not exist, it will be created.\\
 There is also a condition testing for the existence of a child, and even an action to remove a child from a structure variable. There is also a condition testing for the existence of a child, and even an action to remove a child from a structure variable.