如何在名称取决于 int 的循环内创建对象

Question

我有一个名为“Particle”的结构，我想创建几个名称取决于 int 的对象。 由于我在 for 循环中，名称将更改如下：part0、part1、part2。

for (int i = 0; i<num_particles; i++)
{
    //double sample_x, sample_y, sample_theta;
    string name = "part" + std::to_string(i);
    Particle name;
    name.id = i;
    name.x = dist_x(gen);
    name.y = dist_y(gen);
    name.theta = dist_theta(gen);

    cout << "Sample" << " " << name.x << " " << name.y << " " << name.theta << endl;

}

你可以想象这种方法行不通，你有什么解决办法吗？

我已经更新了我的问题，现在这是我的新方法：

我创建了一个向量和一个 int “粒子数”：

std::vector<Particle> particles;

及功能码：

void ParticleFilter::init(double x, double y, double theta, double std[]) {
// TODO: Set the number of particles. Initialize all particles to first position (based on estimates of 
//   x, y, theta and their uncertainties from GPS) and all weights to 1. 
// Add random Gaussian noise to each particle.
// NOTE: Consult particle_filter.h for more information about this method (and others in this file).


default_random_engine gen;
normal_distribution<double> dist_x(x, std[0]);
normal_distribution<double> dist_y(y, std[1]);
normal_distribution<double> dist_theta(theta, std[2]);

//for (int i = 0; i<num_particles; i++)
//{
    //double sample_x, sample_y, sample_theta;
    //string name = "part";
    //+ std::to_string(i);
    //Particle particles;
    particles[num_particles].id =num_particles;
    particles[num_particles].x = dist_x(gen);
    particles[num_particles].y = dist_y(gen);
    particles[num_particles].theta = dist_theta(gen);
    num_particles++;
    cout << "Sample" << " " << particles[num_particles].x  << " " << particles[num_particles].y  << " " << particles[num_particles].theta  << endl;

//}

}

但它还不起作用，它输出“Segmentation fault”。

Answer 1

您可以简单地在您的代码中使用cstdlib 的itoa() 函数。

for (int i = 0; i<10; i++)
{ 
 char a[max];
 string pa="part_";
string name = pa + itoa(i,a,i+1) ;
cout << "Sample" << " " << name << endl;

}
}

样本输出：

 Sample part_0
 Sample part_1
 Sample part_2
 Sample part_3
 Sample part_4
 Sample part_5
 Sample part_6
 Sample part_7
 Sample part_8
 Sample part_9

Answer 2

这个结构存在于 C++ 中，它被称为std::vector。

 // we want to have a bunch of variables of type Particle
 // all named particles[i] for i == 0,1,2....
 std::vector<Particle> particles;

 // create a new particle variable
 particles.emplace_back(x, y, theta);

 // print the variable number 42
 std::cout << particles[42];

Answer 3

为什么要走上var0、var1、var2等变量命名的混乱之路？我建议创建一个数组或向量。

从您的代码 sn-p 中不清楚为什么需要创建具有不同名称的变量。此外，您的代码/用例与变量范围的概念不符。