Module: gears.cache

Cache object with data that can be garbage-collected.

Here is an example with a basic cache:

Usage example output:

new entry created with value 0
0
new entry created with value 1
42
new entry created with value 2
84
0

Usage:

  •  local test_cache = cache.new(function(test)
     -- let's just print about what we created
     print("new entry created with value " .. test)
     -- Pretend this is some expensive computation
     return test * 42
 end)
 -- Populate the cache
 print(test_cache:get(0))
 print(test_cache:get(1))
 print(test_cache:get(2))
 -- no message since it exists
 print(test_cache:get(0))

 The example below demonstrates how the garbage collector will clear the
 cache:




**Usage example output**:

    cache object #0 for first
    cache object #1 for second
    cache object #0 for first
    forcing a garbage collect
    cache object #2 for first
    cache object #3 for second


  • local function tostring_for_cache(obj)
    return obj[1]
end
local counter = 0
local wrapper_cache = gears.cache.new(function(arg)
    local kind = "cache object #" .. tostring(counter) .. " for " .. tostring(arg)
    counter = counter + 1
    return setmetatable({ kind }, { __tostring = tostring_for_cache })
end)
print(wrapper_cache:get("first"))
print(wrapper_cache:get("second"))
-- No new object since it already exists
print(wrapper_cache:get("first"))
print("forcing a garbage collect")
-- The GC can *always* clear the cache
collectgarbage("collect")
print(wrapper_cache:get("first"))
print(wrapper_cache:get("second"))

Info:

  • Copyright: 2015 Uli Schlachter
  • Originally authored by: Uli Schlachter
    (Full contributors list available on our github project)

Constructors

gears.cache (creation_cb) Create a new cache object.

Methods

:get (...) Get an entry from the cache, creating it if it's missing.


Constructors

🔗 gears.cache (creation_cb)
Create a new cache object. A cache keeps some data that can be garbage-collected at any time, but might be useful to keep.

Parameters:

Name Type(s) Description
creation_cb Callback that is used for creating missing cache entries.

Returns:

    A new cache object.

Methods

🔗 :get (...)
Get an entry from the cache, creating it if it's missing.

Parameters:

Name Type(s) Description
... Arguments for the creation callback. These are checked against the cache contents for equality.

Returns:

    The entry from the cache
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