GML中点符号使用疑问及tooltip脚本报错求助

问题背景 #

本人有Python及少量C语言基础，刚接触GML，编写了tooltip脚本，调用时出现<unknown_object>.this未设置错误，以下是脚本代码及报错信息，想确认脚本写法是否正确并解决报错：

原Tooltip脚本代码 #

function tooltip() {
    var this = {};
    
    this.__init__ = function() {
        this.box = [];
        this.cx = obj_cursor.x;
        this.cy = obj_cursor.y;
    }
    
    this.update = function() {
        this.cx = obj_cursor.x;
        this.cy = obj_cursor.y;
    }
    
    this.create_id = function() {
        used_ids = []
        for (var i = 0; i < array_length(this.box); i++) {
            array_push(used_ids, (this.box[i])._id);
        }
        if (array_length(used_ids) == 0) return 0;
        
        array_sort(used_ids, true);
        
        for (var i = 0; i < array_last(used_ids); i++) {
            if (!array_contains(used_ids, i)) return i;
        }
        return array_length(this.box);
    }
    
    this.create_box = function(_x, _y, _w, _h, _title, _desc, _state = false, _pict = spr_office) {
        var _box = {
        pos_x : _x,
        pos_y : _y,
        width : _w,
        height : _h,
        title : _title,
        desc : _desc,
        state : _state,
        pict : _pict,
        _id : this.create_id()
        }
        array_insert(this.box, _box._id, _box);
    }
    
    this.delete_box = function(box_id) {
        for (var i = 0; i < array_length(this.box); i++) {
            if ((this.box[i])._id == box_id) {
                array_delete(this.box, i, 1)
                break; 
            }
        }
    }
    
    this.print = function(box_id) {
        var _data = {};
        for (var i = 0; i < array_length(this.box); i++) {
            if ((this.box[i])._id == box_id) {
                _data = this.box[i];
                break;
            }
        }
        
        var _x = _data.pos_x;
        var _y = _data.pos_y;
        var _w = _data.width;
        var _h = _data.height;
        var _t = _data.title;
        var _d = _data.desc;
        var _p = _data.pict;
        var _col = _data.state ? c_white : c_gray;
        
        draw_rectangle_colour(_x - 2, _y - 2, _x + _w+ 2, _y + _h + 2, c_white, c_white, c_white, c_white, false);
        draw_sprite_stretched_ext(_p, -1, _x, _y, _w, _h, _col, 1);
        
        if ((_x <= this.cx && this.cx <= _x + _w) && (_y <= this.cy && this.cy <= _y + _h)) {
            draw_set_colour(c_black);
            draw_rectangle(this.cx, this.cy, this.cx + _w + 6, this.cy + _h + 6, false);
            draw_set_colour(c_white);
            draw_text_ext(this.cx + 3, this.cy + 3, _d, string_height("Ay"), 150);
        }
    }
    
    this.get_value = function(box_id, target) {
        var _data = {}
        for (var i = 0; i < array_length(this.box); i++) {
            if ((this.box[i])._id == box_id) {
                _data = this.box[i];
                break;
            }
        }
        switch (target) {
            case "pos_x" : return _data.pos_x;
            case "pos_y" : return _data.pos_y;
            case "width" : return _data.width;
            case "height" : return _data.height;
            case "title" : return _data.title;
            case "desc" : return _data.desc;
            case "state" : return _data.state;
            case "pict" : return _data.pict;
            case "_id" : return _data._id;
        }
    }
    this.get_length = function() { return array_length(this.box); }
    this.get_ids = function() {
        _arr = []
        for (var i = 0; i < array_length(this.box); i++) {
            array_push(_arr, (this.box[i])._id);
        }
        return _arr;
    }
    
    return this;
}

报错信息 #

ERROR in action number 1

of Create Event for object obj_ach_manager:

Variable <unknown_object>.this(100048, -2147483648) not set before reading it.

 at gml_Script_anon@95@tooltip@tooltip (line 9) -       this.box = [];

gml_Script_anon@95@tooltip@tooltip (line 9)

gml_Object_obj_ach_manager_Create_0 (line 2) - t.__init__();

错误原因 #

GML中直接调用对象的方法（如t.__init__()）时，方法内部的this不会自动绑定到该对象实例——这和Python的类方法绑定逻辑完全不同。你这里的__init__方法里的this没有指向创建的t实例，导致访问this.box时找不到有效对象，触发报错。

修复方案 #

方式1：临时修复——手动绑定this调用方法 #

修改obj_ach_manager的Create事件代码，用with语句或method函数强制绑定实例：

// 方式1-1：用with语句
t = tooltip();
with(t) {
    __init__();
}

// 方式1-2：用method函数绑定
t = tooltip();
method(t, t.__init__)();

方式2：彻底重构——使用GML官方构造函数语法（推荐） #

GML提供了专门的构造函数写法（带constructor关键字），更符合语言特性，能从根源避免this绑定问题，同时代码更简洁：

function tooltip() constructor {
    // 直接在这里初始化属性，替代原__init__方法
    box = [];
    cx = obj_cursor.x;
    cy = obj_cursor.y;

    update = function() {
        cx = obj_cursor.x;
        cy = obj_cursor.y;
    }

    create_id = function() {
        var used_ids = []; // 新增var，避免全局变量污染
        for (var i = 0; i < array_length(box); i++) {
            array_push(used_ids, box[i]._id);
        }
        if (array_length(used_ids) == 0) return 0;
        
        array_sort(used_ids, true);
        
        for (var i = 0; i < array_last(used_ids); i++) {
            if (!array_contains(used_ids, i)) return i;
        }
        return array_length(box);
    }

    create_box = function(_x, _y, _w, _h, _title, _desc, _state = false, _pict = spr_office) {
        var _box = {
            pos_x : _x,
            pos_y : _y,
            width : _w,
            height : _h,
            title : _title,
            desc : _desc,
            state : _state,
            pict : _pict,
            _id : create_id()
        }
        array_insert(box, _box._id, _box);
    }

    delete_box = function(box_id) {
        for (var i = 0; i < array_length(box); i++) {
            if (box[i]._id == box_id) {
                array_delete(box, i, 1);
                break; 
            }
        }
    }

    print = function(box_id) {
        var _data = {};
        for (var i = 0; i < array_length(box); i++) {
            if (box[i]._id == box_id) {
                _data = box[i];
                break;
            }
        }
        
        var _x = _data.pos_x;
        var _y = _data.pos_y;
        var _w = _data.width;
        var _h = _data.height;
        var _t = _data.title;
        var _d = _data.desc;
        var _p = _data.pict;
        var _col = _data.state ? c_white : c_gray;
        
        draw_rectangle_colour(_x - 2, _y - 2, _x + _w + 2, _y + _h + 2, c_white, c_white, c_white, c_white, false);
        draw_sprite_stretched_ext(_p, -1, _x, _y, _w, _h, _col, 1);
        
        if ((_x <= cx && cx <= _x + _w) && (_y <= cy && cy <= _y + _h)) {
            draw_set_colour(c_black);
            draw_rectangle(cx, cy, cx + _w + 6, cy + _h + 6, false);
            draw_set_colour(c_white);
            draw_text_ext(cx + 3, cy + 3, _d, string_height("Ay"), 150);
        }
    }

    get_value = function(box_id, target) {
        var _data = {};
        for (var i = 0; i < array_length(box); i++) {
            if (box[i]._id == box_id) {
                _data = box[i];
                break;
            }
        }
        switch (target) {
            case "pos_x" : return _data.pos_x;
            case "pos_y" : return _data.pos_y;
            case "width" : return _data.width;
            case "height" : return _data.height;
            case "title" : return _data.title;
            case "desc" : return _data.desc;
            case "state" : return _data.state;
            case "pict" : return _data.pict;
            case "_id" : return _data._id;
        }
    }

    get_length = function() { return array_length(box); }

    get_ids = function() {
        var _arr = []; // 新增var，避免全局变量污染
        for (var i = 0; i < array_length(box); i++) {
            array_push(_arr, box[i]._id);
        }
        return _arr;
    }
}

调用时直接使用new关键字创建实例，无需手动调用初始化方法：

// 在obj_ach_manager的Create事件中
t = new tooltip();

额外注意事项 #

• 原脚本中部分变量未加var声明（如used_ids、_arr），会自动成为全局变量，容易引发不可预见的问题，修复后的代码已补充var声明。
• GML的构造函数语法是官方推荐的面向对象实现方式，比手动模拟对象的写法更稳定、高效。

内容的提问来源于stack exchange，提问作者Ayeah755