c++ - how to count not deleted instances in array of instances? -


i have array of instances in code, :

class squad : public isquad {     public:         squad(void);         squad(squad const & src);         virtual ~squad(void);          int             getcount(void) const;         int             push(ispacemarine*);         ispacemarine*   getunit(int) const;          ispacemarine**              getunits(void) const;         int                         getcapacity(void) const;          squad &     operator=(squad const & rhs);          private:         ispacemarine    **_units; // here array of instances         int const       _squadcapacity;  };

initialized in constructor

squad::squad(void) : _units(new ispacemarine*[64]), _squadcapacity(64) {     return; }

first, the way ?

if yes, try count number of valid instances in array (not null, not deleted) don't know how check if _units[20] deleted example.

how can ?

he current way do:

int                         squad::getcount(void) const {     int     count = 0;     while (this->_units[count] != null && count < this->_squadcapacity)         count++;     return count; } 

    ispacemarine    **_units; // here array of instances     int const       _squadcapacity;

- first, the way ?

no, not way go , neatly shows why std containers , smart pointers big improvement.

with smart pointers express , deal ownership automatically.

i impression squad manages spacemarines, in case should use std::unique_ptr. squad like

class squad : public isquad {   public:     size_t             getcount() const;     void             push(ispacemarine&&);     using spacemarineiterator = std::vector<std::unique_ptr<spacemarine>>::iterator;     // typedef/using iterator appropriate.     spacemarineiterator getunit(int) const;     // ,     spacemarineiterator begin() const;     spacemarineiterator end() const;      size_t                         getcapacity() const;     // no need copy assign either.     //squad &     operator=(squad const & rhs);        private:     std::vector<std::unique_ptr<ispacemarine>> units;   // no need capacity.  };

now, if need different model ownership can std::shared_ptr , std::weak_ptr. model should make effort work std::unique_ptr though.

note: don't discard possibility of using

std::vector<spacemarine> units;

Comments

Post a Comment

Popular posts from this blog

'hasOwnProperty' in javascript -

i use obj.hasownproperty judge whether object has property, when replaced obj[prop] !== undefined , not normal implementation, ask, why behind method can not use it? object.hasownproperty(prop); object[prop] !== undefined; obj[prop] !== undefined wrong 2 reasons: you can explicitly set property undefined , obj[prop] = undefined; . obj.hasownproperty(prop) return true in case. obj[prop] follow prototype chain, return property that's inherited. obj.hasownproperty(prop) returns true if property exists directly in object, returns false inherited properties.
Read more

How to put a lock and transaction on table using spring 4 or above using jdbcTemplate and annotations like @Transactional? -

i trying put lock on table while writing on table , if happened in between roll-back . trying convert below code lock table test_g1 read; lock table test_g write; -- begin; start transaction; insert test_g1 values(143); insert test_g values(145); select * test_g1; select * test_g; rollback; select * test_g; unlock tables; how convert above code @transactional spring jdbctemplate code? @transactional(rollbackfor={dataaccessexception.class}) public void test(){ jdbctemplate.execute("insert test1 (id, nam) values (4, 'a')"); throw new dataaccessexception("error") { }; } here trying throw error, insert statement should rollback it's not happening . thanks edit-1 attaching code , doing in jdbcdaoimpl.java , mentioned problem comment above test() . app.java package com.cgiri.javabrains.spring4; import org.springframework.beans.factory.annotation.autowired; import org.springframework.context.applic...
Read more

How to understand 2 main() functions after using uftrace to profile the C++ program? -

i trying uftrace profile following simple c++ program: #include <iostream> class { public: a() {std::cout << "a created" << std::endl;} ~a() {std::cout << "a destroyed" << std::endl;} }; int main() { a; return 0; } the profile result this: # uftrace a.out created destroyed # duration tid function 2.026 [ 4828] | __cxa_atexit(); [ 4828] | main() { [ 4828] | __static_initialization_and_destruction_0() { 89.397 [ 4828] | std::ios_base::init::init(); 0.768 [ 4828] | __cxa_atexit(); 93.029 [ 4828] | } /* __static_initialization_and_destruction_0 */ 94.425 [ 4828] | } /* main */ [ 4828] | main() { [ 4828] | a::a() { 11.104 [ 4828] | std::operator <<(); 10.825 [ 4828] | std::basic_ostream::operator <<(); 24.514 [ 4828] | } /* a::a */ [ 4828] | a::~a() { 0.978 [ 4828] | ...
Read more