0
我想从QJsonArray中删除所有元素,并且遇到比我想象的更麻烦的事情。这里是我的代码:删除QJsonArray中的所有元素
void Assessment::clearQJsonArray(QJsonArray *array) {
printQJsonArray(*array);
for(int i=0;i<array->count();i++) {
array->removeAt(i);
}
qDebug() << "Test clear:" << array->count();
printQJsonArray(*array);
}
void Assessment::printQJsonArray(QJsonArray array) {
QJsonDocument doc;
doc.setArray(array);
qDebug() << doc.toJson();
}
void Assessment::testClearQJsonArray() {
QJsonArray array;
QJsonObject obj1, obj2, obj3, obj4;
obj1.insert("number",1);
obj2.insert("number",2);
obj3.insert("number",3);
obj4.insert("number",4);
array.append(obj1);
array.append(obj2);
array.append(obj3);
array.append(obj4);
qDebug() << "Before clear";
qDebug() << "Test size:" << array.count();
QJsonObject element;
for(int i=0;i<array.count();i++) {
element = array.at(i).toObject();
qDebug() << element.value("number").toInt();
}
clearQJsonArray(&array);
qDebug() << "After clear";
for(int i=0;i<array.count();i++) {
element = array.at(i).toObject();
qDebug() << element.value("number").toInt();
}
qDebug() << "Test size:" << array.count();
}
而且我得到这样的输出:
(void Assessment::testClearQJsonArray()): Before clear
(void Assessment::testClearQJsonArray()): Test size: 4
(void Assessment::testClearQJsonArray()): 1
(void Assessment::testClearQJsonArray()): 2
(void Assessment::testClearQJsonArray()): 3
(void Assessment::testClearQJsonArray()): 4
(void Assessment::printQJsonArray(QJsonArray)): "[\n {\n \"number\": 1\n },\n {\n \"number\": 2\n },\n {\n \"number\": 3\n },\n {\n \"number\": 4\n }\n]\n"
(void Assessment::clearQJsonArray(QJsonArray*)): Test clear: 2
(void Assessment::printQJsonArray(QJsonArray)): "[\n {\n \"number\": 2\n },\n {\n \"number\": 4\n }\n]\n"
(void Assessment::testClearQJsonArray()): After clear
(void Assessment::testClearQJsonArray()): 2
(void Assessment::testClearQJsonArray()): 4
(void Assessment::testClearQJsonArray()): Test size: 2
我真的不明白为什么对象1和3被删除,但不是2和4。任何想法?
谢谢。
怎么样'*阵列= QJsonArray {};'? – nwp
非常感谢! – highvoltage379
@nwp是的,这绝对应该工作。问题的关键在于这个问题实际上不是关于'QJsonArray',而是与这样的任何容器有关。程序员应该明白像上面这样的_why_代码是不正确的,以避免将来出现这样的错误。奇怪的是'QJsonArray'没有'clear()'这样的东西,所以你的变体是这种情况下最短的。 –