QT notes on qmap container freeing memory

in the light of QMap、QVector Wait for container memory release problem , For beginners , It's really easy to ignore .

The reason I noticed this problem was when I first used... In my project QMap<xx,xxx> The container can store data normally , But when you need to QMap After the content of is cleared , Insert again and there appears Segment error （segment fault） problem .

QMap<QString,Struct node>  test;
/************* . . .  A series of insertion actions are carried out in the middle  ************/
test.clear();

QMap The built-in clear() Emptying the interface has a drawback , Although you can empty QMap Data in , But the memory space is not empty , It will not be cleared until the end of the program , Now , If you keep emptying the insert , It will lead to the continuous increase of memory .

terms of settlement

Some people say they use the Internet Qt Built in function interface qDeleteAll () To clear .
But I found that this seems to be only for the container with value Value with pointer , Can be used qDeleteAll() To clear memory .

// Tolerable 
QMap<int,Struct node*> a;
qDeleteAll(a);

// No good , Will report a mistake 
QMap<int,Struct node> a;
qDeleteAll(a);

The method I use swap function

QMap<int,Struct node> test;
QMap<int,Struct node>().swap(test);
// If used swap() function , Then you don't have to use clear() Function