Skip to main content

lifecycle

lua_std

Trait lifecycle 

Source 
pub trait lifecycle {
    // Provided methods
    fn __gc(&self) { ... }
    fn __close(&self, errobj: any) { ... }
    fn __mode(&self) -> string { ... }
    fn __metatable(&self) -> any { ... }
}
Expand description

Metamethods controlling the life cycle of a value.

Provided Methods§

Source

fn __gc(&self)

The finalizer: called by the garbage collector when the value is collected, if the metatable had a __gc field when it was set.

§Examples
setmetatable({}, { __gc = function() print("collected") end })
collectgarbage()    --> collected
Source

fn __close(&self, errobj: any)

Called when the value, used as a to-be-closed variable (local x <close> = ...), goes out of scope.

§Examples
do
  local guard <close> = setmetatable({}, {
    __close = function() print("closed") end,
  })
  print("inside")
end
--> inside
--> closed
Source

fn __mode(&self) -> string

A metavalue controlling how the value behaves as a weak table: "k" for weak keys, "v" for weak values, "kv" for both.

§Examples
local cache = setmetatable({}, { __mode = "k" })   -- weak keys
cache[{}] = "value"
collectgarbage()
print(next(cache))    --> nil   (the key was collected)
Source

fn __metatable(&self) -> any

If present, protects the metatable: getmetatable returns this metavalue instead, and setmetatable raises an error.

§Examples
local t = setmetatable({}, { __metatable = "locked" })
print(getmetatable(t))            --> locked
print(pcall(setmetatable, t, {}))  --> false   cannot change a protected metatable

Dyn Compatibility§

This trait is dyn compatible.

In older versions of Rust, dyn compatibility was called "object safety".

Implementors§