mirror of
https://github.com/CPunch/Cosmo.git
synced 2024-11-25 16:40:15 +00:00
105 lines
4.2 KiB
Markdown
105 lines
4.2 KiB
Markdown
# Objects & Protos
|
|
|
|
Cosmo supports an eccentric form of Object-Oriented Programming through the use of Objects and Proto-Objects. Under the hood, these are the same datatype, however they can be chained to describe behaviors in relation to other Objects, operators, and provide stateful functions.
|
|
|
|
For example, the following is a proto description for a Range Iterator Object, much akin to python's `range()`.
|
|
|
|
```
|
|
proto Range
|
|
func __init(self, x)
|
|
self.max = x
|
|
end
|
|
|
|
// __iter expects an iterable object to be returned (an object with __next defined)
|
|
func __iter(self)
|
|
self.i = 0
|
|
return self
|
|
end
|
|
|
|
func __next(self)
|
|
if self.i >= self.max then
|
|
return nil // exit iterator loop
|
|
end
|
|
|
|
return self.i++
|
|
end
|
|
end
|
|
```
|
|
|
|
Which, combined with the for-each loop, can produce behavior like python's `range()` iterator
|
|
|
|
```
|
|
for i in Range(5) do
|
|
print(i)
|
|
end
|
|
```
|
|
|
|
Output:
|
|
```
|
|
0
|
|
1
|
|
2
|
|
3
|
|
4
|
|
```
|
|
|
|
When an object is called using the `()` operator, `__init` is called and a new Object is created, with the Proto defined as the called Object. If the object does not have the `__init` field defined, an error is thrown.
|
|
|
|
## Getting, setting & invoking
|
|
|
|
Objects hold fields, these fields can be grabbed using the '.' operator. Conversely, fields can also be set using the '.' and '=' operators. For example:
|
|
|
|
```
|
|
let object = {
|
|
field = "Hello world"
|
|
}
|
|
|
|
object.x = 3
|
|
print(object.field .. ", " .. object.x)
|
|
```
|
|
> Hello world, 3
|
|
|
|
Objects have two main ways of being declared, first was just shown in the above example. The second is through the 'proto' keyword, which is reminiscent of a class-like declaration.
|
|
|
|
```
|
|
proto Test
|
|
func __init(self)
|
|
// __init is required for an object to be instantiated, the 'self' passed is the
|
|
// newly allocated object with it's proto already set
|
|
end
|
|
|
|
func print(self)
|
|
print(self)
|
|
end
|
|
end
|
|
|
|
let objTest = Test()
|
|
|
|
// the ':' operator is used to invoke a method. if the '.' operator is used instead, the
|
|
// raw closure will be given meaning the 'self' parameter won't be populated
|
|
objTest:print()
|
|
|
|
objTest.print(objTest) // equivalent to invoking with ':'
|
|
```
|
|
|
|
When calling methods on objects (like the example above shows) the ':' operator is used to get the method of an object. Without ':' the raw field would be returned, which is a closure.
|
|
|
|
## Reserved Fields and Metamethods
|
|
|
|
Reserved fields are fields that are reserved for describing object behavior. Metamethods are reserved methods for objects
|
|
that are called on special operators.
|
|
|
|
| Field | Type | Behavior |
|
|
| ------------ | ------------------------------------------------ | ----------------------------------------------------------- |
|
|
| __init | `(<object>, ...)` | Newly crafted object is passed, called on instantiation |
|
|
| __newindex | `(<object>, key, newValue)` | Called on new index using the '[] = ' operator |
|
|
| __index | `(<object>, key)` -> `value` | Called on index using the '[]' operator |
|
|
| __equal | `(<object>, <object>)` -> `<boolean>` | Called on equality fail if both protos have the same `__equal` metamethod defined |
|
|
| __tostring | `(<object>)` -> `<string>` | Called when tostring() is called on an object |
|
|
| __tonumber | `(<object>)` -> `<number>` | Called when tonumber() is called on an object |
|
|
| __count | `(<object>)` -> `<number>` | Called when object is used with the '#' count operator |
|
|
| __iter | `(<object>)` -> `<object>` | Called when used in a for-each loop with the 'in' operator |
|
|
| __next | `(<object>)` -> `...` | Called on each iteration in a for-each loop, return values are passed as parameters in the loop |
|
|
| __getter | `[<string> fieldName : <function> getterMethod]` | Indexed & called on field get using the '.' operator |
|
|
| __setter | `[<string> fieldName : <function> setterMethod]` | Indexed & Called on field set using the '.' & '=' operators |
|
|
> -> means 'returns' |