如何使用数据库中的数据填充 QCombobox

QSqlTableModel *QSqlRelationalTableModel:: relationModel(int column) const

返回一个QSqlTableModel用于访问其列是外键的表的对象，如果此列没有关系，则返回 nullptr。

import sys
from PyQt5 import QtSql
from PyQt5.Qt import *


class Dialog(QDialog):
    def __init__(self, dict_category):                      # +++ dict_category
        super().__init__()
        self.setWindowTitle('Input Dialog')
        
        self.line_edit_name = QLineEdit()
        self.line_edit_quantity = QLineEdit()
# !!!
#        self.line_edit_category = QLineEdit()
        self.combobox_category = QComboBox()                              # +++
        self.combobox_category.addItems([name for name in dict_category]) # +++

        form_layout = QFormLayout()
        form_layout.addRow('Name:', self.line_edit_name)
        form_layout.addRow('quantity:', self.line_edit_quantity)
# !!!
        form_layout.addRow('category:', self.combobox_category)           # +++

        button_box = QDialogButtonBox(
            QDialogButtonBox.Ok | QDialogButtonBox.Cancel)
        button_box.accepted.connect(self.accept)
        button_box.rejected.connect(self.reject)

        main_layout = QVBoxLayout(self)
        main_layout.addLayout(form_layout)
        main_layout.addWidget(button_box)


class Example(QMainWindow):
    def __init__(self):
        super().__init__()

        self.createConnection()
        self.fillTable()  # !!!
        self.createModel()
        self.initUI()
        
# +++ vvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvvv        
        self.model_category  = self.model.relationModel(2)   # QtSql.QSqlTableModel
        print(f'm_cat tableName == {self.model_category.tableName()}')
        print(f'm_cat rowCount  == {self.model_category.rowCount()}')
        
        self.dict_category = {}
        for row in range(self.model_category.rowCount()):
            r = self.model_category.record(row)
            id =  r.value(0) 
            name = r.value(1)
            self.dict_category[name] = id
# +++ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

        self.centralWidget = QWidget()
        self.setCentralWidget(self.centralWidget)
        btnAdd = QPushButton("&Добавить запись")
        btnAdd.clicked.connect(self.addRecord)
        btnDel = QPushButton("&Удалить запись")
        btnDel.clicked.connect(self.delRecord)

        layout = QVBoxLayout(self.centralWidget)
        layout.addWidget(self.view)
        layout.addWidget(btnAdd)
        layout.addWidget(btnDel)

    def createConnection(self):
        self.db = QtSql.QSqlDatabase.addDatabase("QSQLITE")
        self.db.setDatabaseName("test_1318914.db") # !!! .db
        if not self.db.open():
            print("Cannot establish a database connection")
            return False

    def fillTable(self):
        self.db.transaction()
        q = QtSql.QSqlQuery()
        #                             vvvvvvvv
        q.exec_("DROP TABLE IF EXISTS category;")
        q.exec_("CREATE TABLE category (id INT PRIMARY KEY, catname TEXT);")
        q.exec_("INSERT INTO category VALUES (1, 'Расходники');")
        q.exec_("INSERT INTO category VALUES (2, 'Носители');")

        #                             vvvv
        q.exec_("DROP TABLE IF EXISTS good;")
        q.exec_("CREATE TABLE good (Name TEXT, Quantity INT, Category INT);")
        q.exec_("INSERT INTO good VALUES ('Барабан для принтера', 8, 1);")
        q.exec_("INSERT INTO good VALUES ('Бумага для принтера', 3, 1);")
        q.exec_("INSERT INTO good VALUES ('Дискета', 10, 2);")
        self.db.commit()

    def createModel(self):
        self.model = QtSql.QSqlRelationalTableModel()
        self.model.setTable("good")
        self.model.setHeaderData(0, Qt.Horizontal, "Название")
        self.model.setHeaderData(1, Qt.Horizontal, "Кол-во")
        self.model.setHeaderData(2, Qt.Horizontal, "Категория")
        self.set_relation()
        self.model.select()

    def initUI(self):
        self.view = QTableView()
        self.view.setModel(self.model)
        self.view.setColumnWidth(0, 150)
        mode = QAbstractItemView.SingleSelection
        self.view.setSelectionMode(mode)

    def closeEvent(self, event):
        if (self.db.open()):
            self.db.close()

    def set_relation(self):
        self.model.setRelation(2, QtSql.QSqlRelation(
            "category",
            "id",
            "catname"
        ))

# !!!
    def addRecord(self):
        inputDialog = Dialog(self.dict_category)      # +++ self.dict_category
        rez = inputDialog.exec()
        if not rez:
            msg = QMessageBox.information(self, 'Внимание', 'Диалог сброшен.')
            return

        name = inputDialog.line_edit_name.text()
        quantity = inputDialog.line_edit_quantity.text()
# !!! combobox_category       
#        category = inputDialog.line_edit_category.text()
        category = self.dict_category[
            inputDialog.combobox_category.currentText()
        ]
# +++ ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
        
        if (not name) or (not quantity) or (not category):
            msg = QMessageBox.information(self,
                'Внимание', 'Заполните пожалуйста все поля.')
            return

        r = self.model.record()
        r.setValue(0, name)
        r.setValue(1, int(quantity))
        r.setValue(2, int(category))

        self.model.insertRecord(-1, r)
        self.model.select()

    def delRecord(self):
        row = self.view.currentIndex().row()
        if row == -1:
            msg = QMessageBox.information(self,
                'Внимание', 'Выберите запись для удаления.')
            return

        name = self.model.record(row).value(0)
        quantity = self.model.record(row).value(1)
        category = self.model.record(row).value(2)

        inputDialog = Dialog(self.dict_category)          # +++ self.dict_category
        inputDialog.setWindowTitle('Удалить запись ???')
        inputDialog.line_edit_name.setText(name)
        inputDialog.line_edit_quantity.setText(str(quantity))
# !!!        inputDialog.line_edit_category.setText(str(category))
#        inputDialog.line_edit_category.setText(str(category))
        inputDialog.combobox_category.setCurrentText(str(category))  # +++

        rez = inputDialog.exec()
        if not rez:
            msg = QMessageBox.information(self, 'Внимание', 'Диалог сброшен.')
            return

        self.model.setRelation(2, QtSql.QSqlRelation())
        self.model.select()
        self.model.removeRow(row)
        self.set_relation()
        self.model.select()

        msg = QMessageBox.information(self, 'Успех', 'Запись удалена.')


if __name__ == '__main__':
    app = QApplication(sys.argv)
    w = Example()
    w.setWindowTitle("QRelationalSqlTableModel")
    w.resize(430, 250)
    w.show()
    sys.exit(app.exec_())

总的来说，决定已经来了 =) 逻辑如下：

1. 我们创建了一个函数，该函数将从数据库fill_combobox()中读取一个表category并返回一个格式为 ['1 Consumables', '2 Media'] 的列表，其中一个分隔符由空格分隔，以便稍后可以提取该数字以写入 id

2. 将列表传递给对话框构造函数并填充QComboBox

3. 我们考虑文本currentText，通过拆分我们将获取列表的第一个元素。用户感到满意和高兴 =))) 通过标记#<---的更改地点的代码

import sys
from PyQt5 import QtSql
from PyQt5.Qt import *


class Dialog(QDialog):
    def __init__(self, list_for_combo=[]):
        super().__init__()
        self.setWindowTitle('Input Dialog')
        self.line_edit_name = QLineEdit()
        self.line_edit_quantity = QLineEdit()
        self.q_combo_category = QComboBox() #<---
        self.q_combo_category.addItems(list_for_combo)#<---

        form_layout = QFormLayout()
        form_layout.addRow('Name:', self.line_edit_name)
        form_layout.addRow('quantity:', self.line_edit_quantity)
        form_layout.addRow('category:', self.q_combo_category)#<---

        button_box = QDialogButtonBox(
            QDialogButtonBox.Ok | QDialogButtonBox.Cancel)
        button_box.accepted.connect(self.accept)
        button_box.rejected.connect(self.reject)

        main_layout = QVBoxLayout(self)
        main_layout.addLayout(form_layout)
        main_layout.addWidget(button_box)


class Example(QMainWindow):
    def __init__(self):
        super().__init__()

        self.createConnection()
        self.fillTable()  # !!!
        self.createModel()
        self.initUI()

        self.centralWidget = QWidget()
        self.setCentralWidget(self.centralWidget)
        btnAdd = QPushButton("&Добавить запись")
        btnAdd.clicked.connect(self.addRecord)
        btnDel = QPushButton("&Удалить запись")
        btnDel.clicked.connect(self.delRecord)

        layout = QVBoxLayout(self.centralWidget)
        layout.addWidget(self.view)
        layout.addWidget(btnAdd)
        layout.addWidget(btnDel)

    def createConnection(self):
        self.db = QtSql.QSqlDatabase.addDatabase("QSQLITE")
        self.db.setDatabaseName("test_1318914.db")  # !!! .db
        if not self.db.open():
            print("Cannot establish a database connection")
            return False

    def fillTable(self):
        self.db.transaction()
        q = QtSql.QSqlQuery()
        #                             vvvvvvvv
        q.exec_("DROP TABLE IF EXISTS category;")
        q.exec_("CREATE TABLE category (id INT PRIMARY KEY, catname TEXT);")
        q.exec_("INSERT INTO category VALUES (1, 'Расходники');")
        q.exec_("INSERT INTO category VALUES (2, 'Носители');")

        #                             vvvv
        q.exec_("DROP TABLE IF EXISTS good;")
        q.exec_("CREATE TABLE good (Name TEXT, Quantity INT, Category INT);")
        q.exec_("INSERT INTO good VALUES ('Барабан для принтера', 8, 1);")
        q.exec_("INSERT INTO good VALUES ('Бумага для принтера', 3, 1);")
        q.exec_("INSERT INTO good VALUES ('Дискета', 10, 2);")
        self.db.commit()

    def createModel(self):
        self.model = QtSql.QSqlRelationalTableModel()
        self.model.setTable("good")
        self.model.setHeaderData(0, Qt.Horizontal, "Название")
        self.model.setHeaderData(1, Qt.Horizontal, "Кол-во")
        self.model.setHeaderData(2, Qt.Horizontal, "Категория")
        self.set_relation()
        self.model.select()

    def initUI(self):
        self.view = QTableView()
        self.view.setModel(self.model)
        self.view.setColumnWidth(0, 150)
        mode = QAbstractItemView.SingleSelection
        self.view.setSelectionMode(mode)

    def closeEvent(self, event):
        if (self.db.open()):
            self.db.close()

    def set_relation(self):
        self.model.setRelation(2, QtSql.QSqlRelation(
            "category",
            "id",
            "catname"
        ))

    def addRecord(self):

        def fill_combobox():#<---
            list_name = []#<---
            query = QSqlQuery('SELECT * FROM category')#<---
            while query.next():#<---
                list_name.append(str(query.value(0))+" "+query.value(1))#<---
            query.exec_()#<---
            return list_name#<---

        list_name = fill_combobox()#<---

        inputDialog = Dialog(list_for_combo= list_name)#<---
        rez = inputDialog.exec()
        if not rez:
            msg = QMessageBox.information(self, 'Внимание', 'Диалог сброшен.')
            return

        name = inputDialog.line_edit_name.text()
        quantity = inputDialog.line_edit_quantity.text()
        q_combo_category = inputDialog.q_combo_category.currentText()#<---
        category = q_combo_category.split()[0]#<---
        if (not name) or (not quantity) or (not category):
            msg = QMessageBox.information(self,
                                          'Внимание', 'Заполните пожалуйста все поля.')
            return

        r = self.model.record()
        r.setValue(0, name)
        r.setValue(1, int(quantity))
        r.setValue(2, int(category))

        self.model.insertRecord(-1, r)
        self.model.select()

    def delRecord(self):
        row = self.view.currentIndex().row()
        if row == -1:
            msg = QMessageBox.information(self,
                                          'Внимание', 'Выберите запись для удаления.')
            return

        name = self.model.record(row).value(0)
        quantity = self.model.record(row).value(1)
        category = self.model.record(row).value(2)

        inputDialog = Dialog()
        inputDialog.setWindowTitle('Удалить запись ???')
        inputDialog.line_edit_name.setText(name)
        inputDialog.line_edit_quantity.setText(str(quantity))
        inputDialog.line_edit_category.setText(str(category))
        rez = inputDialog.exec()
        if not rez:
            msg = QMessageBox.information(self, 'Внимание', 'Диалог сброшен.')
            return

        self.model.setRelation(2, QtSql.QSqlRelation())
        self.model.select()
        self.model.removeRow(row)
        self.set_relation()
        self.model.select()

        msg = QMessageBox.information(self, 'Успех', 'Запись удалена.')


if __name__ == '__main__':
    app = QApplication(sys.argv)
    w = Example()
    w.setWindowTitle("QRelationalSqlTableModel")
    w.resize(430, 250)
    w.show()
    sys.exit(app.exec_())