使用QMap并获取编译错误消息

Question

我正在尝试在类原型中使用"QMap"：

QMap<QString, TargetsInfo*> m_targets;

在一种访问方法中，我有：

TargetsInfo* TargetsModel::addTarget(int division, int camera, int map) const {
TargetsInfo* target = getTarget(division, camera, map);
if (target == nullptr) {
const QString key = makeKey(division, camera, map);
target = new TargetsInfo();
if ( target != nullptr ) {
m_targets.insert(key, target);
}
}
return target;
}
TargetsInfo* TargetsModel::getTarget(int division, int camera, int map) const {
const QString key = makeKey(division, camera, map);
QMap<QString, TargetsInfo*>::iterator itr = m_targets.find(key);
return (its == m_targets.end()) ? nullptr : itr.value();
}

当我编译时，我得到了以下错误，我正在努力找出错误：

C2663: 'QMap<QString, TargetInfo *>::insert': 2 overloads have no legal conversion for 'this' pointer
C2440: 'initialising': cannot convert from 'QMap<QString, TargetInfo *>::const_iterator' to 'QMap::<QString, TargetInfo *>::iterator'
No constructor could take the source type, or constructor overload resolution was ambiguous

Answer 1

对于第二次错误更改

QMap<QString, TargetsInfo*>::iterator itr = ...

至

QMap<QString, TargetsInfo*>::const_iterator itr = ...

您的getTarget方法是const，因此m_targets.find返回一个const迭代器(否则您可以在假定的const方法中更改m_targets(。

对于第一个错误，请从addTarget方法中删除const。显然，向m_targets添加项的方法不应该是常量。