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lua:meta [2015/07/19 13:20] – niziaklua:meta [2016/07/14 08:50] – [Metamethods] niziak
Line 32: Line 32:
 </code> </code>
  
-IF mettables are normal table, so it is possible to use the same table also as metatable to save some resources+If mettables are normal table, so it is possible to use the same table also as metatable to save some resources
 <code lua> <code lua>
 setmetatable (NormalTable, NormalTable) setmetatable (NormalTable, NormalTable)
 +</code>
 +
 +**setmetatable(table, metatable)** returns its first argument, so it is possible to simplify code below:
 +<code lua>
 +local NormalTable = {}
 +setmetatable (NormalTable, NormalTable)
 +</code>
 +to
 +<code lua>
 +local NormalTable = setmetatable ({}, {})
 </code> </code>
  
 ===== Metamethods ===== ===== Metamethods =====
-  * **%%__index%%** is called when key in table doesn't exists. **%%__index%%** can be a function or another table - fallback table. Fallback table can have metatable which points to another fallback table and so on. It is possible to create very long fallback table chain. +[[http://lua-users.org/wiki/MetatableEvents]] 
-  * **%%__newindex%%** is called when value to not existsing key (contains **nil**) is assigned. If key exists, method is not called. + 
-  * **%%__metatable%%** +[[http://lua-users.org/wiki/MetamethodsTutorial]]   
 + 
 +  * **%%__index%%** - is called when key in table is accessed. **%%__index%%** can be a function or another table - fallback table. Fallback table can have metatable which points to another fallback table and so on. It is possible to create very long fallback table chain. 
 +    * **%%__index%% = function (table, key)**, return value of fucntion is returned as result. 
 +    * **%%__index%% = table** 
 +    * to access table key without invoking %%__index%% methamethod use **rawget(table,key)** 
 + 
 +  * * **%%__newindex%%** is called when new value is assigned to key key 
 +    * **%%__newindex%% = function (table, key ,value)** 
 +    * to set new value without invoking methamethod, use **rawset(table, key, value)** 
 + 
 +  * **%%__metatable%%** when set, metatable is hidden. Value of **%%__metatable%%** is returned instead of original metatable.
   * **%%__call%%** - if somebady calls table as function, this metamethod will be called   * **%%__call%%** - if somebady calls table as function, this metamethod will be called
-  * **%%__tostring%%** - +  * **%%__tostring%%** - when **tostring(table)** is called 
 +  * **%%__len%%**
  
 ===== Synctatic sugar ===== ===== Synctatic sugar =====
Line 65: Line 87:
 class:method(1, 2, 3) class:method(1, 2, 3)
 class.method(t, 1, 2, 3) class.method(t, 1, 2, 3)
-</codE>+</code>