迭代 GtkTreeStore 中的项目

Question

我的 Gtk3 应用程序从 SQLite 数据库读取数据并填充 GtkTreeView (GtkTreeStore)。树视图（应该是）根级别的年（YYYY，字符串）元素列表，以月（MM，字符串）作为子节点：

2000
- 03
- 04
2005
- 01
- 02
- 03
- 04
...

桌子：

CREATE TABLE IF NOT EXISTS year_months (
     id                    INTEGER PRIMARY KEY AUTOINCREMENT,
     year                  TEXT NOT NULL,
     month                 TEXT NOT NULL,
     UNIQUE (year, month)
);

INSERT INTO year_months (year, month) VALUES ('2023', '08');
INSERT INTO year_months (year, month) VALUES ('2023', '01');
INSERT INTO year_months (year, month) VALUES ('2023', '02');
INSERT INTO year_months (year, month) VALUES ('2023', '03');
INSERT INTO year_months (year, month) VALUES ('2023', '04');
INSERT INTO year_months (year, month) VALUES ('2023', '05');
INSERT INTO year_months (year, month) VALUES ('2023', '06');
INSERT INTO year_months (year, month) VALUES ('2023', '07');
INSERT INTO year_months (year, month) VALUES ('2023', '09');
INSERT INTO year_months (year, month) VALUES ('2023', '10');
INSERT INTO year_months (year, month) VALUES ('2022', '10');
INSERT INTO year_months (year, month) VALUES ('2022', '05');
INSERT INTO year_months (year, month) VALUES ('2022', '07');
INSERT INTO year_months (year, month) VALUES ('2022', '09');

SELECT * FROM year_months;

有效。我的树视图现在看起来像：

2023
- 08
2023
- 01
2023
- 02
2023
- 03
...

在

sqlite3_exec()

回调函数（为每一行调用）中，我迭代树（存储）中的每个元素，以检查是否已经存在与获取的行具有相同年份的节点。我将新行附加为现有年份元素的子元素（如果之前已将其添加到树中），或者根据需要创建一个新的顶级节点：

int populate_treeview(void *model, int argc, char **argv, char **azColName) {
   GtkTreeIter iter2;
   gboolean valid = gtk_tree_model_get_iter_first(model, &iter2);
   gchararray myval;
   int match = 0;
   while (valid)
   {
       gtk_tree_model_get(GTK_TREE_MODEL(model), &iter2, YM_YEAR, &myval, -1);
       printf("myval = %s\n", myval);

       if (!strcmp(myval, argv[1])) {
           gtk_tree_store_append(GTK_TREE_STORE(model), &iter2, &iter2);
           gtk_tree_store_set(GTK_TREE_STORE(model), &iter2, YM_YEAR, argv[1], -1);
           gtk_tree_store_set(GTK_TREE_STORE(model), &iter2, YM_MONTH, argv[2], -1);
           match = 1;
           free(myval);
           continue;
       }
       free(myval);
       valid = gtk_tree_model_iter_next(GTK_TREE_MODEL(model), &iter2);
    }
    if (!match) {
        // new year
        gtk_tree_store_append(GTK_TREE_STORE(model), &iter2, NULL);
        gtk_tree_store_set (GTK_TREE_STORE(model), &iter2, YM_YEAR, argv[1], -1);
        gtk_tree_store_set (GTK_TREE_STORE(model), &iter2, YM_MONTH, argv[2], -1);
    }
    return 0;
}

在回调函数中（在添加 while 循环之前）调用

gtk_tree_store_append(GTK_TREE_STORE(model), &iter2, NULL);

有效，所以我知道

model

已正确设置。但是，该代码会导致

get_tree_model_iter_get_first()

:

出现段错误

(PCG:8309): Gtk-WARNING **: 19:54:44.026: gtktreestore.c:338: Invalid type (null)
(PCG:8309): Gtk-CRITICAL **: 19:54:44.027: gtk_tree_model_get_iter_first: assertion 'GTK_IS_TREE_MODEL (tree_model)' failed

我尝试了模型

GTK_TREE_STORE(model)

和

GTK_TREE_MODEL(model)

的演员阵容，但没有成功。