Methods: Difference between revisions
>Flurite fixing some markup |
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Methods are unique functions which belong to a particular object or can be custom made. | Methods are unique functions which belong to a particular object or can be custom made. They are a major focus of Roblox Lua. Some common examples of methods include 'Destroy()', 'Clone()', and 'FindFirstChild()'. You can find a full list of methods [http://wiki.roblox.com/index.php/Category:Methods here]. | ||
A method acts like a function stored within an object. The method itself is accessed in the same way a [[Functions|function]] in a table is accessed. However, a special property of methods changes how they are called. | |||
These two lines of code are equivalent, calling the function < | These two lines of code are equivalent, calling the function <var>a</var> with the parameter <var>b</var>. | ||
<code lua> | |||
b.a(b) | |||
b:a() | |||
</code> | |||
The second is briefer and more concise. Methods can increase typing speed, because there is less need to retype variable names. | The second is briefer and more concise. Methods can increase typing speed, because there is less need to retype variable names. | ||
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First, we need a table to ''apply'' the method to. I'm going to make a checkbox. It doesn't actually do anything, but it's an application example. Feel free to make this work. | First, we need a table to ''apply'' the method to. I'm going to make a checkbox. It doesn't actually do anything, but it's an application example. Feel free to make this work. | ||
<code lua> | |||
Checkbox = { | |||
Checked = false; | |||
CheckedImage = "Image"; | |||
UncheckedImage = "Image"; | |||
ImageButton = ...; | |||
ChangeState = function(self) | |||
self.Checked = not self.Checked | |||
end | |||
} | |||
Checkbox.ImageButton.MouseButton1Down:connect(function() | |||
Checkbox:ChangeState() | |||
end) | |||
</code> | |||
You might think you could type | You might think you could type | ||
<code lua>Checkbox.ImageButton.MouseButton1Down:connect(Checkbox.ChangeState)</code> | |||
However, that would call <code>Checkbox.ChangeState(x, y)</code> when the event fired. We need to call <code>Checkbox.ChangeState(Checkbox)</code>. | However, that would call <code lua>Checkbox.ChangeState(x, y)</code> when the event fired. We need to call <code lua>Checkbox.ChangeState(Checkbox)</code>. | ||
When you call a function as a method, you automatically pass an argument as the TABLE ITSELF. For example, | When you call a function as a method, you automatically pass an argument as the TABLE ITSELF. For example, | ||
<code lua> | |||
function ReturnTable(Num) | |||
return { | |||
Num; | |||
PrintNum = function(self) | |||
print(self.Num) | |||
end | |||
} | |||
end | |||
Tabl = ReturnTable(5) | |||
Tabl:PrintNum() | |||
</code> | |||
That will output 5 because we passed in the table, so the function will receive the table it's located in. Because we called it as a method, it passed "Tabl" as an argument. You can do it with a dot, but it looks kind of stupid: | That will output 5 because we passed in the table, so the function will receive the table it's located in. Because we called it as a method, it passed "Tabl" as an argument. You can do it with a dot, but it looks kind of stupid: | ||
<code lua>Tabl.PrintNum(Tabl)</code> | |||
Revision as of 06:39, 27 January 2012
Methods are unique functions which belong to a particular object or can be custom made. They are a major focus of Roblox Lua. Some common examples of methods include 'Destroy()', 'Clone()', and 'FindFirstChild()'. You can find a full list of methods here.
A method acts like a function stored within an object. The method itself is accessed in the same way a function in a table is accessed. However, a special property of methods changes how they are called.
These two lines of code are equivalent, calling the function a with the parameter b.
b.a(b)
b:a()
The second is briefer and more concise. Methods can increase typing speed, because there is less need to retype variable names.
Making your own
Making your own methods can
- Make your code look cool
- Make your tables more dynamic
First, we need a table to apply the method to. I'm going to make a checkbox. It doesn't actually do anything, but it's an application example. Feel free to make this work.
Checkbox = {
Checked = false;
CheckedImage = "Image";
UncheckedImage = "Image";
ImageButton = ...;
ChangeState = function(self)
self.Checked = not self.Checked
end
}
Checkbox.ImageButton.MouseButton1Down:connect(function()
Checkbox:ChangeState()
end)
You might think you could type
Checkbox.ImageButton.MouseButton1Down:connect(Checkbox.ChangeState)
However, that would call Checkbox.ChangeState(x, y) when the event fired. We need to call Checkbox.ChangeState(Checkbox).
When you call a function as a method, you automatically pass an argument as the TABLE ITSELF. For example,
function ReturnTable(Num)
return {
Num;
PrintNum = function(self)
print(self.Num)
end
}
end
Tabl = ReturnTable(5)
Tabl:PrintNum()
That will output 5 because we passed in the table, so the function will receive the table it's located in. Because we called it as a method, it passed "Tabl" as an argument. You can do it with a dot, but it looks kind of stupid:
Tabl.PrintNum(Tabl)
