Can any body explain me below statement of function ?
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@Qt-embedded-developer said in Can any body explain me below statement of function ?:
And actually it is complex such that i am unable to understand how to delete it ?
So i nee example to delete it.I don't understand what looks complicated to you.
You have to delete the instance when you remove it from map.@KroMignon actually i have seen that already completely developed project never removed it. and never deleted it.
as you can see that how i accessed GetAFCSTicketInstance() in other class.
so where i need to put "delete SqliteManagerBGSync" ?
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@KroMignon actually i have seen that already completely developed project never removed it. and never deleted it.
as you can see that how i accessed GetAFCSTicketInstance() in other class.
so where i need to put "delete SqliteManagerBGSync" ?
@Qt-embedded-developer said in Can any body explain me below statement of function ?:
so where i need to put "delete SqliteManagerBGSync" ?
You could do it in the destructor of the class holding sqliteManagerMap member.
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@KroMignon actually i have seen that already completely developed project never removed it. and never deleted it.
as you can see that how i accessed GetAFCSTicketInstance() in other class.
so where i need to put "delete SqliteManagerBGSync" ?
@Qt-embedded-developer said in Can any body explain me below statement of function ?:
actually i have seen that already completely developed project never removed it. and never deleted it.
as you can see that how i accessed GetAFCSTicketInstance() in other class.
so where i need to put "delete SqliteManagerBGSync" ?As far as I can see,
app::dbmanager::SqliteManagerBGSync::GetDBInstance()seems to be a static method, so I guess the map is also an static member of classapp::dbmanager::SqliteManagerBGSync.
To be totally clean, I would add a static methodcleanup()to this class to clear properly the map:for (const auto& kv : sqliteManagerMap) { delete kv.second; } sqliteManagerMap.clear(); -
@Qt-embedded-developer said in Can any body explain me below statement of function ?:
so where i need to put "delete SqliteManagerBGSync" ?
You could do it in the destructor of the class holding sqliteManagerMap member.
This post is deleted! -
@Qt-embedded-developer said in Can any body explain me below statement of function ?:
actually i have seen that already completely developed project never removed it. and never deleted it.
as you can see that how i accessed GetAFCSTicketInstance() in other class.
so where i need to put "delete SqliteManagerBGSync" ?As far as I can see,
app::dbmanager::SqliteManagerBGSync::GetDBInstance()seems to be a static method, so I guess the map is also an static member of classapp::dbmanager::SqliteManagerBGSync.
To be totally clean, I would add a static methodcleanup()to this class to clear properly the map:for (const auto& kv : sqliteManagerMap) { delete kv.second; } sqliteManagerMap.clear();@KroMignon as you can see from my function that i have taken the local map in function.so on scope get completed this map also get deleted. But there is i think SqliteManagerBGSync() is global which get allocated to memory so i think shall i need to use
delete SqliteManagerBGSync() ; in cleanup() memthod.
May be i am wrong. if it is then please correct me .
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@KroMignon as you can see from my function that i have taken the local map in function.so on scope get completed this map also get deleted. But there is i think SqliteManagerBGSync() is global which get allocated to memory so i think shall i need to use
delete SqliteManagerBGSync() ; in cleanup() memthod.
May be i am wrong. if it is then please correct me .
@Qt-embedded-developer said in Can any body explain me below statement of function ?:
delete SqliteManagerBGSync() ;
Does not make sense and is not valid C++ - you are trying to delete a new stack allocated SqliteManagerBGSync instance...
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@KroMignon as you can see from my function that i have taken the local map in function.so on scope get completed this map also get deleted. But there is i think SqliteManagerBGSync() is global which get allocated to memory so i think shall i need to use
delete SqliteManagerBGSync() ; in cleanup() memthod.
May be i am wrong. if it is then please correct me .
@Qt-embedded-developer said in Can any body explain me below statement of function ?:
SqliteManagerBGSync() is global which get allocated to memory so i think shall i need to use
delete SqliteManagerBGSync() ; in cleanup() memthod.
May be i am wrong. if it is then please correct me .I don't want to hurt, just to know how to help you, but what are your programming skills?
Do you know what are static methods or classes?
According to you code extract,SqliteManagerBGSyncis a class.
I guess methodGetDBInstance()is declared in header as follow:class SqliteManagerBGSync { public: static SqliteManagerBGSync* GetDBInstance(); };Correct or wrong?
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@Qt-embedded-developer said in Can any body explain me below statement of function ?:
delete SqliteManagerBGSync() ;
Does not make sense and is not valid C++ - you are trying to delete a new stack allocated SqliteManagerBGSync instance...
@jsulm So then just let me know this local map allocated the dynamic memory to class when and how to delete it with example. still i am misinterpret it then let me know.
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@Qt-embedded-developer said in Can any body explain me below statement of function ?:
SqliteManagerBGSync() is global which get allocated to memory so i think shall i need to use
delete SqliteManagerBGSync() ; in cleanup() memthod.
May be i am wrong. if it is then please correct me .I don't want to hurt, just to know how to help you, but what are your programming skills?
Do you know what are static methods or classes?
According to you code extract,SqliteManagerBGSyncis a class.
I guess methodGetDBInstance()is declared in header as follow:class SqliteManagerBGSync { public: static SqliteManagerBGSync* GetDBInstance(); };Correct or wrong?
@KroMignon yes it is static. thanks. just let me help me how to make this code proper.
Because i have see that my application is get restarted due too much heap utilization.
and i think this above code is reason for that.
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@KroMignon yes it is static. thanks. just let me help me how to make this code proper.
Because i have see that my application is get restarted due too much heap utilization.
and i think this above code is reason for that.
@Qt-embedded-developer said in Can any body explain me below statement of function ?:
yes it is static. thanks. just let me help me how to make this code proper.
Because i have see that my application is get restarted due too much heap utilization.
and i think this above code is reason for that.This code don't look bad to me and I don't think it is the place where heap memory is consuming.
As written before, it will only ensure that you are using the rightSqliteManagerBGSyncfor the current thread and create a newSqliteManagerBGSyncif there is no one already created for current thread. -
@Qt-embedded-developer said in Can any body explain me below statement of function ?:
yes it is static. thanks. just let me help me how to make this code proper.
Because i have see that my application is get restarted due too much heap utilization.
and i think this above code is reason for that.This code don't look bad to me and I don't think it is the place where heap memory is consuming.
As written before, it will only ensure that you are using the rightSqliteManagerBGSyncfor the current thread and create a newSqliteManagerBGSyncif there is no one already created for current thread.@KroMignon means as my static function consist map with local scope. if is okay then i not need to clear it. But query is that though one copy of class member will have allocated memory to class. So whenever it to some task it will occupy some memory. so that memory when to and how to free it ?
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@KroMignon means as my static function consist map with local scope. if is okay then i not need to clear it. But query is that though one copy of class member will have allocated memory to class. So whenever it to some task it will occupy some memory. so that memory when to and how to free it ?
@Qt-embedded-developer said in Can any body explain me below statement of function ?:
means as my static function consist map with local scope. if is okay then i not need to clear it. But query is that allocated memory to class when to and how to free it ?
I don't believe the map
sqliteManagerMapis local, the map must also be static. -
@Qt-embedded-developer said in Can any body explain me below statement of function ?:
means as my static function consist map with local scope. if is okay then i not need to clear it. But query is that allocated memory to class when to and how to free it ?
I don't believe the map
sqliteManagerMapis local, the map must also be static.@KroMignon means i can not free the memory ?
as my function is static, so map taken inside this function is also static and memory allocated to this class also static. if this is true then allocated memory will use heap segment or data segment.
i know as i am unsure about many things it make frustrating for other. sorry for that. Just i want to improve my self.
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@KroMignon means i can not free the memory ?
as my function is static, so map taken inside this function is also static and memory allocated to this class also static. if this is true then allocated memory will use heap segment or data segment.
i know as i am unsure about many things it make frustrating for other. sorry for that. Just i want to improve my self.
@Qt-embedded-developer said in Can any body explain me below statement of function ?:
as my function is static, so map taken inside this function is also static and memory allocated to this class also static. if this is true then allocated memory will use heap segment or data segment.
i know as i am unsure about many things it make frustrating for other. sorry for that. Just i want to improve my self.Please, take time to understand memory allocation and variable/class member scope!
This is very basic C++ knowledge you have to know to be able to program.
There is no magic.In C++, a static class method can only access to static class members or to members of class instances (or global variable of course).
So if GetDBInstance() can have access to sqliteManagerMap, this variable must be static or global. That is all I have say.I am pretty sure; sqliteManagerMap is declared is class header with something like this:
class SqliteManagerBGSync { protected: static std::map<int, SqliteManagerBGSync*> sqliteManagerMap; }; -
@Qt-embedded-developer said in Can any body explain me below statement of function ?:
as my function is static, so map taken inside this function is also static and memory allocated to this class also static. if this is true then allocated memory will use heap segment or data segment.
i know as i am unsure about many things it make frustrating for other. sorry for that. Just i want to improve my self.Please, take time to understand memory allocation and variable/class member scope!
This is very basic C++ knowledge you have to know to be able to program.
There is no magic.In C++, a static class method can only access to static class members or to members of class instances (or global variable of course).
So if GetDBInstance() can have access to sqliteManagerMap, this variable must be static or global. That is all I have say.I am pretty sure; sqliteManagerMap is declared is class header with something like this:
class SqliteManagerBGSync { protected: static std::map<int, SqliteManagerBGSync*> sqliteManagerMap; };@KroMignon said in Can any body explain me below statement of function ?:
static std::map<int, SqliteManagerBGSync*> sqliteManagerMap;
Yes its static.
what happen when this map not declared as static and this map declared inside the static function defination only ?
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@KroMignon said in Can any body explain me below statement of function ?:
static std::map<int, SqliteManagerBGSync*> sqliteManagerMap;
Yes its static.
what happen when this map not declared as static and this map declared inside the static function defination only ?
@Qt-embedded-developer said in Can any body explain me below statement of function ?:
static function defination
A "static function defination" simply means the function/method exists outside any instance of a class. It has no implication for storage.
std::map<int, SqliteManagerBGSync*> sqliteManagerMap;(nostatic) would be just a local variable in the function, destroyed after the function call completes.If you want the map to persist throughout the lifetime of each instance of a class, declare it as a (non-
static) member variable in the class. But then different instances of the class have separate maps, they do not share a single map. -
@Qt-embedded-developer said in Can any body explain me below statement of function ?:
static function defination
A "static function defination" simply means the function/method exists outside any instance of a class. It has no implication for storage.
std::map<int, SqliteManagerBGSync*> sqliteManagerMap;(nostatic) would be just a local variable in the function, destroyed after the function call completes.If you want the map to persist throughout the lifetime of each instance of a class, declare it as a (non-
static) member variable in the class. But then different instances of the class have separate maps, they do not share a single map.@JonB said in Can any body explain me below statement of function ?:
declare it as a (non-static) member variable in the class
i think above sentence is incorrect. it may be static instead non-static.
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@JonB said in Can any body explain me below statement of function ?:
declare it as a (non-static) member variable in the class
i think above sentence is incorrect. it may be static instead non-static.
@Qt-embedded-developer said in Can any body explain me below statement of function ?:
i think above sentence is incorrect.
Pardon? Member variables might be
staticor not. With different lifetime correspondingly. You asked aboutstatic std::map<int, SqliteManagerBGSync*> sqliteManagerMap;"when this map not declared as static ", which I answered. I wrote:If you want the map to persist throughout the lifetime of each instance of a class, declare it as a (non-static) member variable in the class
which is correct. May or may not be what you want, but it's correct....
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@Qt-embedded-developer said in Can any body explain me below statement of function ?:
i think above sentence is incorrect.
Pardon? Member variables might be
staticor not. With different lifetime correspondingly. You asked aboutstatic std::map<int, SqliteManagerBGSync*> sqliteManagerMap;"when this map not declared as static ", which I answered. I wrote:If you want the map to persist throughout the lifetime of each instance of a class, declare it as a (non-static) member variable in the class
which is correct. May or may not be what you want, but it's correct....
@JonB Thanks
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@Qt-embedded-developer said in Can any body explain me below statement of function ?:
i want to know the what is technical meaning of below statement
sqliteManagerMap.insert(std::pair<int,SqliteManagerBGSync>(threadId,new SqliteManagerBGSync()));
shall i need to free memory allocated to SqliteManagerBGSync() ?I think the idea between this is to get access to DB connection which has been created for the current thread (as QSqlDatabase has to be used in the thread in which it has been created).
But to answer to your question, yes you have to free used memory.
The easiest way to do it, would be to use smart pointer, likeQSharedPointer==> useQSharedPointer<SqliteManagerBGSync>instead ofSqliteManagerBGSync*.@KroMignon thanks for suggesting smart pointer.
