Package com.smartfoxserver.v2.entities.match

Class MatchExpression

  • All Implemented Interfaces:
    java.io.Serializable
    public class MatchExpression
extends java.lang.Object
implements java.io.Serializable

    Overview

    Match Expressions are built like "if" conditions in any common programming language. They work like queries in a database and can be used to search for Rooms or Users using custom criteria. These expressions are extremely easy to create and concatenate and they can be used for many different filtering operations within the SFS2X framework.

    This is a quick example: 

     MatchExpression exp = new MatchExpression('rank', NumberMatch.GREATER_THAN, 5).and('country', StringMatch.EQUALS, 'Italy')

    Expressions are made of three elements:

    • Variable name
    • Match operator
    • Value
    Additionally any number of expressions can be linked together with a logical AND / OR operator, just like in regular code. In the above example we have created an expression that will check for a rank value > 5 and a country value == "Italy".

    The search options are not just limited to User/Room Variables name. In fact the Matching engine provides two extra classes, RoomProperties and UserProperties, where you can access many specific attributes of the Room and User class.

    This is an example of matching specific Room properties and Variables: 

     // Prepare match expression
 MatchExpression exp = new MatchExpression(RoomProperties.IS_GAME, BoolMatch.EQUALS, true).and
                                        (RoomProperties.HAS_FREE_PLAYER_SLOTS, BoolMatch.EQUALS, true).and
                                        ("isGameStarted", BoolMatch.EQUALS, false);
 
 // Search Rooms
 List<Rooms> joinableRooms = sfsApi.findRooms(zone.getRoomListFromGroup("chess"), exp, 0);

    Advanced features

    the Match expression offer advanced capabilities of searching through nested data structures such as SFSObject and SFSArray. This is done via a very simple dot-syntax. Here's an example of how it works: 
     MatchExpression exp = new MatchExpression("europe.italy.capital", StringMatch.EQUALS, "Rome")

    The above example goes down deep into an SFSObject called europe, taking the italy object (another SFSObject) and finally reading its String field capital and matching it with another String. Here is one more examples using SFSObject and SFSArray: 

     MatchExpression exp = new MatchExpression("europe.italy.majorCities.3.name", StringMatch.EQUALS, "Milan")

    From the italy object we obtain a majorCities SFSArray and we grab the third item in it (the .3 expression means 'give me the element at index == 3'). The item is again an SFSObject whose name property we finally compare to a String.

    The power of Match Expression doesn't end here. You can run multiple passes of matching if you need complex searches to be performed. For example you can run a first match and obtain a list of filtered Rooms and then use it to apply another expression to further refine your search, and so on and so forth.
    Also you will learn more interesting usages of Match Expressions in conjunction with the SFSGame class later in this very article.

    See Also:
    RoomProperties, UserProperties, Serialized Form

    • Constructor Summary

      Constructors 
      Constructor Description
      MatchExpression​(java.lang.String varName, com.smartfoxserver.v2.entities.match.IMatcher condition, java.lang.Object value)  

    • Method Summary

      All Methods Static Methods Instance Methods Concrete Methods 
      Modifier and Type Method Description
      MatchExpression and​(java.lang.String varName, com.smartfoxserver.v2.entities.match.IMatcher condition, java.lang.Object value)
      Concatenates two expressions with the logical AND operator.
      static MatchExpression fromSFSArray​(ISFSArray sfsa)  
      boolean hasNext()
      Check if the current expression is concatenated to another one via a logic operator
      MatchExpression next()
      Get the next expression chained to the current one.
      MatchExpression or​(java.lang.String varName, com.smartfoxserver.v2.entities.match.IMatcher condition, java.lang.Object value)
      Concatenates two expressions with the logical OR operator.
      MatchExpression rewind()
      Rewinds the cursor to the first expression in the chain and return the MatchExpression at the top of the chain of expressions
      ISFSArray toSFSArray()
      private
      java.lang.String toString()  

      • Methods inherited from class java.lang.Object

        clone, equals, finalize, getClass, hashCode, notify, notifyAll, wait, wait, wait

    • Constructor Detail

      • MatchExpression

        public MatchExpression​(java.lang.String varName,
                       com.smartfoxserver.v2.entities.match.IMatcher condition,
                       java.lang.Object value)

    • Method Detail

      • and

        public MatchExpression and​(java.lang.String varName,
                           com.smartfoxserver.v2.entities.match.IMatcher condition,
                           java.lang.Object value)
        Concatenates two expressions with the logical AND operator.
        Parameters:
        varName - name of the variable or property
        condition - the match condition
        value - the value to match
        Returns:
        the new resulting MatchExpression
        See Also:
        LogicOperator

      • or

        public MatchExpression or​(java.lang.String varName,
                          com.smartfoxserver.v2.entities.match.IMatcher condition,
                          java.lang.Object value)
        Concatenates two expressions with the logical OR operator.
        Parameters:
        varName - name of the variable or property
        condition - the match condition
        value - the value to match
        Returns:
        the new resulting MatchExpression
        See Also:
        LogicOperator

      • toString

        public java.lang.String toString()
        Overrides:
        toString in class java.lang.Object

      • hasNext

        public boolean hasNext()
        Check if the current expression is concatenated to another one via a logic operator
        Returns:
        true if the current expression is concatenated to another one via a logic operator
        See Also:
        LogicOperator

      • next

        public MatchExpression next()
        Get the next expression chained to the current one.
        Returns:
        the next expression chained to the current one.

      • rewind

        public MatchExpression rewind()
        Rewinds the cursor to the first expression in the chain and return the MatchExpression at the top of the chain of expressions
        Returns:
        the MatchExpression at the top of the chain of expressions

      • toSFSArray

        public ISFSArray toSFSArray()
        private