std::shared_ptr<T>::operator bool

 

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std::shared_ptr

成員函式

shared_ptr::shared_ptr

shared_ptr::~shared_ptr

shared_ptr::operator=

修改器

shared_ptr::reset

shared_ptr::swap

觀察器

shared_ptr::get

shared_ptr::operator*shared_ptr::operator->

shared_ptr::operator[] (C++17)

shared_ptr::use_count

shared_ptr::unique (C++20之前已棄用，C++20中移除*)

shared_ptr::operator bool

shared_ptr::owner_before

shared_ptr::owner_hash (C++26)

shared_ptr::owner_equal (C++26)

非成員函式

swap(std::shared_ptr)

make_sharedmake_shared_for_overwrite (C++20 起)

allocate_sharedallocate_shared_for_overwrite (C++20 起)

static_pointer_castdynamic_pointer_castconst_pointer_castreinterpret_pointer_cast (C++17)

get_deleter

operator==operator!=operator<operator<=operator>operator>=operator<=> (until C++20)(until C++20)(until C++20)(until C++20)(until C++20)(C++20)

operator<<

atomic_xxx 函式 (C++20中已棄用，C++26中移除*)

輔助類

atomic<std::shared_ptr> (C++20)

hash<std::shared_ptr>

推導指南(C++17)

 

explicit operator bool() const noexcept;

檢查 *this 是否儲存非空指標，即 get() != nullptr 是否為真。

引數

(無)

返回值

如果 *this 儲存指標，則返回 true，否則返回 false。

注意

一個空的 shared_ptr（其中 use_count() == 0）可能儲存一個可透過 get() 訪問的非空指標，例如如果它是使用別名建構函式建立的。

示例

執行此程式碼

#include <iostream>
#include <memory>
 
void report(std::shared_ptr<int> ptr) 
{
    if (ptr)
        std::cout << "*ptr=" << *ptr << "\n";
    else
        std::cout << "ptr is not a valid pointer.\n";
}
 
int main()
{
    std::shared_ptr<int> ptr;
    report(ptr);
 
    ptr = std::make_shared<int>(7);
    report(ptr);
}

輸出

ptr is not a valid pointer.
*ptr=7

參閱

get	返回儲存的指標 (public member function)