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Foreachkey

The foreachkey construct provides another way to iterate over vectors and maps. It is used to execute some code for each index or key in a given container.

Syntax#

Source code (UnigineScript)
foreachkey(key_variable; map; loop_increment) {
	// some_code;
 }

Parts#

  • key_variable is the current key (or index). The internal container cursor is moved to point at the next key-value pair (or indexed item).
  • The type of key_variable doesn't matter.
  • loop_increment is executed at the end of each iteration. It is optional.

Examples#

  • Source code (UnigineScript)
    int map[] = ( "begin" : "flower", "middle" : "fruit", "end" : "tree" );
    foreachkey(int i; map) {
    	log.message("%s\t=>\t%s\n",i,map[i]);
    }
    The result is:
    Output
    begin   =>      flower
    end     =>      tree
    middle  =>      fruit
  • Source code (UnigineScript)
    int map[] = ( "begin" : "flower", "middle" : "fruit", "end" : "tree" );
    foreachkey(int i, j = 0; map; j++) {
    	log.message("%d: %s\t=>\t%s\n",j,i,map[i]);
    }
    The result is:
    Output
    0: begin   =>      flower
    1: end     =>      tree
    2: middle  =>      fruit
Notice
Before the execution keys are sorted in the ascending order.

Modifications of keys inside the foreachkey block do not affect the map, however, values can be modified directly.

Source code (UnigineScript)
int map[] = ( "begin" : "flower", "middle" : "fruit", "end" : "tree" );
foreachkey(int i; map) {
	i = "first";	// it doesn't affect the map
	map[i] = -9.6;	// it's ok, map is changed
}

Nesting foreachkey#

In case foreachkey structure is called within another foreachkey structure, for each block a copy of the map should be stored. (Such approach allows for higher performance.)

Source code (UnigineScript)
int map[] = ( "1" : "head", "2" : "foot" );

int copy[];
copy.copy(map);

foreachkey(int i; map) {
	foreachkey(int j; copy)	// foreachkey(int j; map) will generate an error
	{
		log.message("%s\t->\t%s\t%s\t->\t%s\n",i,map[i],j,map[j]);
	}
}
The output of the example is:
Output
1	->	head	1	->	head
1	->	head    2	->	foot
2	->	foot	1	->	head
2	->	foot	2	->	foot
Last update: 2018-12-27