搜索结构向量 [英] Search vector of structs

问题描述

我试图在结构向量中找到一个字符串.但是我一直收到错误消息，错误消息太长，所以我将其上传到外部.其中一部分是

I'm trying to find a string within in a vector of structs. But I keep getting an error, the error message is way too long so Ill upload it externally. A part of it is

"错误:'operator==' 不匹配(操作数类型为 'char' 和 'const std::__cxx11::basic_string'){ 返回 *__it == _M_value;}"

"error: no match for 'operator==' (operand types are 'char' and 'const std::__cxx11::basic_string') { return *__it == _M_value; }"

我目前使用的代码是:

struct constants {
    std::string name, lastname;
    float salary=0;
};

void searchPerson(const std::vector<constants> &search) {
    using namespace std;
    vector<constants>name;
    string searchTerm;
    cout << "Enter last name of the person you wish you lookup." << "\n";
    cin >> searchTerm;
for (size_t k=0; k<name.size(); k++){
    if (std::find(name[k].lastname.begin(), name[k].lastname.end(), searchTerm) != name[k].lastname.end())
    {
        cout << "Test" << "\n";
    }
  }
}

我似乎无法让它工作，我不知道出了什么问题.最终目标是让用户输入一个人的姓氏，如果程序中存储了一个姓氏的人，它将打印该人的所有信息(名字、姓氏和薪水).我可能还会使用相同的搜索技术从程序中删除一个人.

I just cant seem to get it working, I don't know whats wrong. The end goal is to let the user input the last name of a person, if theres a person with that last name stored in the program, it will print all the information about that person (first name, last name and salary). I will probably also be using the same search technique to delete a person from the program.

我可以通过简单地使用 for 循环轻松地使其工作，但使用 find 语法肯定是有原因的，下面的代码片段很神奇.

I can easily get it working by simply using a for loop, but there should definitely be a reason for using the find syntax, The below snippet work wonders.

for (size_t i=0; i<name.size(); i++) {
    if (name[i].lastname== searchTerm)
        cout << "Test" << "\n";
}

https://pastebin.com/mk0pTWgr

推荐答案

没有按照您的想法去做.这是一个 for 循环，它迭代 constants 的向量，并尝试在每个 constants 对象的 lastname 内进行搜索.我认为你不是故意这样做的.您可以像这样简单地将 lastname 与 searchTerm 进行比较:

The isn't doing what you think it is. It's a for loop that iterates a vector of constants and tries to search within lastname of each individual constants object. I don't think you mean to do this. You can simply compare the lastname with searchTerm like this:

for (size_t k = 0; k < name.size(); k++) {
    if (name[k].lastname == searchTerm)
    {
        std::cout << "Test" << "\n";
        break;
    }
}

但是，最好避免使用像 std::vector 这样的 stl 集合来手工制作 for 循环.您可以使用 std::find 但这会在您的结构中使用 operator == .您要么必须提供，要么可以使用 std::find_if 代替并提供一个谓词函数来进行比较:

However, hand-crafted for loops are best avoided with stl collections like std::vector. You could use std::find but that will make use of an operator == within your struct. You will either have to provide or you could use std::find_if instead and supply a predicate function to do the comparison:

if (std::find_if(name.cbegin(), name.cend(),
        [&searchTerm](const constants& c) { return searchTerm == c.lastname; }) != name.end())
{
    std::cout << "Test" << "\n";
}

这将避免使用 for 循环.请注意，lambda 函数是谓词，它通过引用捕获您的 searchTerm 并将其仅与 lastname 进行比较.

This will avoid the use of a for loop. Note that a lambda function is the predicate, which captures your searchTerm by reference and compares it with lastname only.

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