std::remove_if

【1】std::remove_if

今天突然有同事问下面这段代码应如何理解。

源码如下：

void GStiffenerBlockRepoDefaultImpl::destory(int id) noexcept
{
    m_stiffeners.erase(std::remove_if(std::begin(m_stiffeners), std::end(m_stiffeners), [&](auto s)->bool {
        return s.id == id; 
    }), std::end(m_stiffeners));
}

【2】应用示例

用代码说话，比讲解更容易理解。请看如下示例与运行结果：

（1）示例程序

#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
using namespace std;

int main()
{
    vector<string> srcStr = { "apple", "banana", "key", "cat", "dog", "orange", "banana", "pig", "dog", "monkey" };

    auto printSrc = [&]() {
        int index = 0;
        for (auto& item : srcStr)
        {
            cout << (index++) << "|" << item << " ";
        }
    };

    cout << "*************************************************" << endl;
    cout << "the original element of vector size :: " << srcStr.size() << endl;
    cout << "the original element of vector :: " << endl;
    printSrc();
    cout << endl << "*************************************************" << endl;

    cout << endl << "+++++++++++++++++++++++++++++++++++++++++++++++++" << endl;
    auto find_str = "banana";
    auto sd = remove_if(srcStr.begin(), srcStr.end(), [&](string element) { return element == find_str; });
    cout << "after remove banana size :: " << srcStr.size() << endl;
    cout << "after remove banana :: " << endl;
    printSrc();

    int index = 0;
    vector<string>::iterator iter = sd;
    cout << endl << "before erase banana, prepare to erase data :: " << endl;
    for (; iter != srcStr.end(); ++iter)
    {
        cout << (index++) << "|" << *iter << " ";
    }

    srcStr.erase(sd, srcStr.end());
    cout << endl << "after erase banana size :: " << srcStr.size() << endl;
    cout << "after erase banana data :: " << endl;
    printSrc();
    cout << endl << "+++++++++++++++++++++++++++++++++++++++++++++++++" << endl;

    cout << endl << "=================================================" << endl;
    find_str = "dog";
    srcStr.erase(remove_if(srcStr.begin(), srcStr.end(),
        [&](string element) { return element == find_str; }),
        srcStr.end());
    
    cout << "after erase dog size :: " << srcStr.size() << endl;
    cout << "after erase dog data :: " << endl;
    printSrc();
    cout << endl << "=================================================" << endl;

    return 0;
}

（2）运行结果

【3】总结

（1）

（2）