Useful GMS2 Code Snippets

A page of useful code snippets.

approach script:

I call this “subcompact approach script”

var x += clamp(target-x, -max_spd, max_spd);

In function form:

// approach(value, target, amount)
return argument0 + clamp(argument1 - argument0, -argument2, argument2);

debug helper script:

var str = "";
for(var i=0; i<argument_count; i++) {
    str += string(argument[i]);
}
show_debug_message(str);

This script makes it easier to write debug messages by automatically stringifying the arguments. e.g. instead of:show_debug_message("X: " + string(x) + " Y: " + string(y)); use scr_debug("X: ", x, " Y: ", y);

ds_maps: iterating through a map:

var key = ds_map_find_first(<ds_map>);
while(not is_undefined(key)) { 
    var value = ds_map_find_value(<ds_map>, key);
    // do stuff
    key = ds_map_find_next(<ds_map>, key);
}

babyjeans version:

for(var key=ds_map_find_first(<ds_map>); not is_undefined(key); key=ds_map_find_next(<ds_map>, key)) { 
    var value = ds_map_find_value(<ds_map>, key);
    // do stuff
}

IDE detect:

Detect if the code is running inside the IDE (as this sometimes breaks extensions):

if(debug_mode) return true; // if debug_mode, we’re definitely in IDE
if(code_is_compiled()) return false; // if compiled, we’re definitely not
if(parameter_count() == 3 and parameter_string(1) == “-game”) return true; // this tests for the IDE’s runner
return false; // I guess not

JSON: loading from file:

var buff = buffer_load(<filename>);
map = json_decode(buffer_read(buff, buffer_text));
buffer_delete(buff);

With error checking:

var buff = buffer_load(<filename>);
map = json_decode();
if(map == -1) {
    // json decode error
}
buffer_delete(buff);

JSON: saving to file:

var str = json_encode(<map_name>);
var buff = buffer_create(string_byte_length(str), buffer_fixed, 1);
buffer_write(buff, buffer_text, str);
buffer_save(buff, <filename>);
buffer_delete(buff)

Singleton: pattern (with error popup in debug mode):

if(instance_number(object_index) > 1) {
    if(debug_mode) {
        show_error("More than one "+object_get_name(object_index)+" exists in "+room_get_name(room), true);
    }
    else {
        instance_destroy();
        exit;
    }
}

This code snippet prevents more than one instance from being in a given room (e.g. in case of accidentally placing a persistent object twice, or returning to a room containing a persistent object). Either shows an error in debug mode, or silently destroys the instance that tries to be created.

Wrap (or handling negative modulo)

Wrapping between 0 and max:

/// wrap (value, max)
return (argument0 % argument1 + argument1) % argument1;

Some work would be needed to make this work with any (including negative) values; or a range