copy_if() with lambda expression

本文通过一个C++代码示例展示了如何使用标准库函数`copy_if`结合`vector`容器来筛选出大于特定阈值的元素,并将结果输出到控制台。此示例有助于理解STL算法的应用及lambda表达式的使用。

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#include <iostream>
#include <vector>
#include <algorithm>

using namespace std;

int main()
{
    vector<int> ivec = { 1, 2, 101, 102, 8, 9, 104};
    vector<int> ivec2;
    int limit = 100;
    copy_if(ivec.begin(), ivec.end(), back_inserter(ivec2),
            [limit](int v){return v>limit;});

    for_each(ivec2.begin(), ivec2.end(), [](int elem){cout << elem << " "; });
    return 0;
}

下面函数添加到chromium源码中用于获取cookie,函数: void FindSiteCookies(Profile* profile, const std::string& domain) { // 获取 CookieManager network::mojom::CookieManager* cookie_manager = profile->GetDefaultStoragePartition()->GetCookieManagerForBrowserProcess(); // 构建查询选项 net::CookieOptions options; options.set_include_httponly(); // 包含 HttpOnly Cookie options.set_same_site_cookie_context(net::CookieOptions::SameSiteCookieContext::MakeInclusive()); // 异步获取 Cookie 列表 cookie_manager->GetCookieList(GURL("https://" + domain), options, net::CookiePartitionKeyCollection(), base::BindOnce([](const net::CookieAccessResultList& cookies, const net::CookieAccessResultList& excluded_cookies) { for (const auto& cookie : cookies) { LOG(INFO) << "Found cookie: " << cookie.cookie.Name() << "=" << cookie.cookie.Value() << " for domain: " << cookie.cookie.Domain(); } })); } 报错: ../../chrome/browser/ui/toolbar/app_menu_model.cc(1775,90): error: member access into incomplete type 'StoragePartition' 1775 | network::mojom::CookieManager* cookie_manager = profile->GetDefaultStoragePartition()->GetCookieManagerForBrowserProcess(); | ^ ../..\content/public/browser/browser_context.h(106,7): note: forward declaration of 'content::StoragePartition' 106 | class StoragePartition; | ^ ../../chrome/browser/ui/toolbar/app_menu_model.cc(1783,19): error: member access into incomplete type 'network::mojom::CookieManager' 1783 | cookie_manager->GetCookieList(GURL("https://" + domain), options, net::CookiePartitionKeyCollection(), | ^ ../..\components/signin/public/base/signin_client.h(40,7): note: forward declaration of 'network::mojom::CookieManager' 40 | class CookieManager; | ^ ../../chrome/browser/ui/toolbar/app_menu_model.cc(1783,76): error: no member named 'CookiePartitionKeyCollection' in namespace 'net' 1783 | cookie_manager->GetCookieList(GURL("https://" + domain), options, net::CookiePartitionKeyCollection(), | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~ ../../chrome/browser/ui/toolbar/app_menu_model.cc(1785,37): error: variable '__begin2' cannot be implicitly captured in a lambda with no capture-default specified 1785 | for (const auto& cookie : cookies) { | ^ ../../chrome/browser/ui/toolbar/app_menu_model.cc(1784,124): note: while substituting into a lambda expression here 1784 | base::BindOnce([](const net::CookieAccessResultList& cookies, const net::CookieAccessResultList& excluded_cookies) { | ^ ../../chrome/browser/ui/toolbar/app_menu_model.cc(1785,37): note: '__begin2' declared here 1785 | for (const auto& cookie : cookies) { | ^ ../../chrome/browser/ui/toolbar/app_menu_model.cc(1784,24): note: lambda expression begins here 1784 | base::BindOnce([](const net::CookieAccessResultList& cookies, const net::CookieAccessResultList& excluded_cookies) { | ^ ../../chrome/browser/ui/toolbar/app_menu_model.cc(1784,25): note: capture '__begin2' by value 1784 | base::BindOnce([](const net::CookieAccessResultList& cookies, const net::CookieAccessResultList& excluded_cookies) { | ^ | __begin2 ../../chrome/browser/ui/toolbar/app_menu_model.cc(1784,25): note: capture '__begin2' by reference 1784 | base::BindOnce([](const net::CookieAccessResultList& cookies, const net::CookieAccessResultList& excluded_cookies) { | ^ | &__begin2 ../../chrome/browser/ui/toolbar/app_menu_model.cc(1784,25): note: default capture by value 1784 | base::BindOnce([](const net::CookieAccessResultList& cookies, const net::CookieAccessResultList& excluded_cookies) { | ^ | = ../../chrome/browser/ui/toolbar/app_menu_model.cc(1784,25): note: default capture by reference 1784 | base::BindOnce([](const net::CookieAccessResultList& cookies, const net::CookieAccessResultList& excluded_cookies) { | ^ | & ../../chrome/browser/ui/toolbar/app_menu_model.cc(1785,37): error: variable '__end2' cannot be implicitly captured in a lambda with no capture-default specified 1785 | for (const auto& cookie : cookies) { | ^ ../../chrome/browser/ui/toolbar/app_menu_model.cc(1785,37): note: '__end2' declared here ../../chrome/browser/ui/toolbar/app_menu_model.cc(1784,24): note: lambda expression begins here 1784 | base::BindOnce([](const net::CookieAccessResultList& cookies, const net::CookieAccessResultList& excluded_cookies) { | ^ ../../chrome/browser/ui/toolbar/app_menu_model.cc(1784,25): note: capture '__end2' by value 1784 | base::BindOnce([](const net::CookieAccessResultList& cookies, const net::CookieAccessResultList& excluded_cookies) { | ^ | __end2 ../../chrome/browser/ui/toolbar/app_menu_model.cc(1784,25): note: capture '__end2' by reference 1784 | base::BindOnce([](const net::CookieAccessResultList& cookies, const net::CookieAccessResultList& excluded_cookies) { | ^ | &__end2 ../../chrome/browser/ui/toolbar/app_menu_model.cc(1784,25): note: default capture by value 1784 | base::BindOnce([](const net::CookieAccessResultList& cookies, const net::CookieAccessResultList& excluded_cookies) { | ^ | = ../../chrome/browser/ui/toolbar/app_menu_model.cc(1784,25): note: default capture by reference 1784 | base::BindOnce([](const net::CookieAccessResultList& cookies, const net::CookieAccessResultList& excluded_cookies) { | ^ | & ../../chrome/browser/ui/toolbar/app_menu_model.cc(1785,37): error: variable '__begin2' cannot be implicitly captured in a lambda with no capture-default specified 1785 | for (const auto& cookie : cookies) { | ^ ../../chrome/browser/ui/toolbar/app_menu_model.cc(1785,37): note: '__begin2' declared here ../../chrome/browser/ui/toolbar/app_menu_model.cc(1784,24): note: lambda expression begins here 1784 | base::BindOnce([](const net::CookieAccessResultList& cookies, const net::CookieAccessResultList& excluded_cookies) { | ^ ../../chrome/browser/ui/toolbar/app_menu_model.cc(1784,25): note: capture '__begin2' by value 1784 | base::BindOnce([](const net::CookieAccessResultList& cookies, const net::CookieAccessResultList& excluded_cookies) { | ^ | __begin2 ../../chrome/browser/ui/toolbar/app_menu_model.cc(1784,25): note: capture '__begin2' by reference 1784 | base::BindOnce([](const net::CookieAccessResultList& cookies, const net::CookieAccessResultList& excluded_cookies) { | ^ | &__begin2 ../../chrome/browser/ui/toolbar/app_menu_model.cc(1784,25): note: default capture by value 1784 | base::BindOnce([](const net::CookieAccessResultList& cookies, const net::CookieAccessResultList& excluded_cookies) { | ^ | = ../../chrome/browser/ui/toolbar/app_menu_model.cc(1784,25): note: default capture by reference 1784 | base::BindOnce([](const net::CookieAccessResultList& cookies, const net::CookieAccessResultList& excluded_cookies) { | ^ | & ../../chrome/browser/ui/toolbar/app_menu_model.cc(1786,50): error: variable 'cookie' cannot be implicitly captured in a lambda with no capture-default specified 1786 | LOG(INFO) << "Found cookie: " << cookie.cookie.Name() | ^ ../../chrome/browser/ui/toolbar/app_menu_model.cc(1785,30): note: 'cookie' declared here 1785 | for (const auto& cookie : cookies) { | ^ ../../chrome/browser/ui/toolbar/app_menu_model.cc(1784,24): note: lambda expression begins here 1784 | base::BindOnce([](const net::CookieAccessResultList& cookies, const net::CookieAccessResultList& excluded_cookies) { | ^ ../../chrome/browser/ui/toolbar/app_menu_model.cc(1784,25): note: capture 'cookie' by value 1784 | base::BindOnce([](const net::CookieAccessResultList& cookies, const net::CookieAccessResultList& excluded_cookies) { | ^ | cookie ../../chrome/browser/ui/toolbar/app_menu_model.cc(1784,25): note: capture 'cookie' by reference 1784 | base::BindOnce([](const net::CookieAccessResultList& cookies, const net::CookieAccessResultList& excluded_cookies) { | ^ | &cookie ../../chrome/browser/ui/toolbar/app_menu_model.cc(1784,25): note: default capture by value 1784 | base::BindOnce([](const net::CookieAccessResultList& cookies, const net::CookieAccessResultList& excluded_cookies) { | ^ | = ../../chrome/browser/ui/toolbar/app_menu_model.cc(1784,25): note: default capture by reference 1784 | base::BindOnce([](const net::CookieAccessResultList& cookies, const net::CookieAccessResultList& excluded_cookies) { | ^ | & ../../chrome/browser/ui/toolbar/app_menu_model.cc(1787,31): error: variable 'cookie' cannot be implicitly captured in a lambda with no capture-default specified 1787 | << "=" << cookie.cookie.Value() | ^ ../../chrome/browser/ui/toolbar/app_menu_model.cc(1785,30): note: 'cookie' declared here 1785 | for (const auto& cookie : cookies) { | ^ ../../chrome/browser/ui/toolbar/app_menu_model.cc(1784,24): note: lambda expression begins here 1784 | base::BindOnce([](const net::CookieAccessResultList& cookies, const net::CookieAccessResultList& excluded_cookies) { | ^ ../../chrome/browser/ui/toolbar/app_menu_model.cc(1784,25): note: capture 'cookie' by value 1784 | base::BindOnce([](const net::CookieAccessResultList& cookies, const net::CookieAccessResultList& excluded_cookies) { | ^ | cookie ../../chrome/browser/ui/toolbar/app_menu_model.cc(1784,25): note: capture 'cookie' by reference 1784 | base::BindOnce([](const net::CookieAccessResultList& cookies, const net::CookieAccessResultList& excluded_cookies) { | ^ | &cookie ../../chrome/browser/ui/toolbar/app_menu_model.cc(1784,25): note: default capture by value 1784 | base::BindOnce([](const net::CookieAccessResultList& cookies, const net::CookieAccessResultList& excluded_cookies) { | ^ | = ../../chrome/browser/ui/toolbar/app_menu_model.cc(1784,25): note: default capture by reference 1784 | base::BindOnce([](const net::CookieAccessResultList& cookies, const net::CookieAccessResultList& excluded_cookies) { | ^ | & ../../chrome/browser/ui/toolbar/app_menu_model.cc(1788,43): error: variable 'cookie' cannot be implicitly captured in a lambda with no capture-default specified 1788 | << " for domain: " << cookie.cookie.Domain(); | ^ ../../chrome/browser/ui/toolbar/app_menu_model.cc(1785,30): note: 'cookie' declared here 1785 | for (const auto& cookie : cookies) { | ^ ../../chrome/browser/ui/toolbar/app_menu_model.cc(1784,24): note: lambda expression begins here 1784 | base::BindOnce([](const net::CookieAccessResultList& cookies, const net::CookieAccessResultList& excluded_cookies) { | ^ ../../chrome/browser/ui/toolbar/app_menu_model.cc(1784,25): note: capture 'cookie' by value 1784 | base::BindOnce([](const net::CookieAccessResultList& cookies, const net::CookieAccessResultList& excluded_cookies) { | ^ | cookie ../../chrome/browser/ui/toolbar/app_menu_model.cc(1784,25): note: capture 'cookie' by reference 1784 | base::BindOnce([](const net::CookieAccessResultList& cookies, const net::CookieAccessResultList& excluded_cookies) { | ^ | &cookie ../../chrome/browser/ui/toolbar/app_menu_model.cc(1784,25): note: default capture by value 1784 | base::BindOnce([](const net::CookieAccessResultList& cookies, const net::CookieAccessResultList& excluded_cookies) { | ^ | = ../../chrome/browser/ui/toolbar/app_menu_model.cc(1784,25): note: default capture by reference 1784 | base::BindOnce([](const net::CookieAccessResultList& cookies, const net::CookieAccessResultList& excluded_cookies) { | ^ | & ../../chrome/browser/ui/toolbar/app_menu_model.cc(1784,24): error: no viable conversion from '(lambda at ../../chrome/browser/ui/toolbar/app_menu_model.cc:1784:24)' to '(lambda at ../../chrome/browser/ui/toolbar/app_menu_model.cc:1784:24)' 1784 | base::BindOnce([](const net::CookieAccessResultList& cookies, const net::CookieAccessResultList& excluded_cookies) { | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 1785 | for (const auto& cookie : cookies) { | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 1786 | LOG(INFO) << "Found cookie: " << cookie.cookie.Name() | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 1787 | << "=" << cookie.cookie.Value() | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 1788 | << " for domain: " << cookie.cookie.Domain(); | ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ 1789 | } | ~ 1790 | })); | ~ ../../chrome/browser/ui/toolbar/app_menu_model.cc(1784,24): note: candidate constructor (the implicit copy constructor) not viable: no known conversion from '(lambda at ../../chrome/browser/ui/toolbar/app_menu_model.cc:1784:24)' to 'const (lambda at ../../chrome/browser/ui/toolbar/app_menu_model.cc:1784:24) &' for 1st argument ../../chrome/browser/ui/toolbar/app_menu_model.cc(1784,24): note: candidate constructor (the implicit move constructor) not viable: no known conversion from '(lambda at ../../chrome/browser/ui/toolbar/app_menu_model.cc:1784:24)' to '(lambda at ../../chrome/browser/ui/toolbar/app_menu_model.cc:1784:24) &&' for 1st argument 1784 | base::BindOnce([](const net::CookieAccessResultList& cookies, const net::CookieAccessResultList& excluded_cookies) { | ^ ../../chrome/browser/ui/toolbar/app_menu_model.cc(1784,24): note: candidate function ../..\base/functional/bind.h(58,32): note: passing argument to parameter 'functor' here 58 | inline auto BindOnce(Functor&& functor, Args&&... args) { | ^ 10 error
最新发布
08-22
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