For 循环在 Laravel 控制器类中不起作用
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For Loop Not Working in a Laravel Controller Class
提问by avijit bhattacharjee
In my Laravel project, I have a BusController.php file where I need to run a for() loop. However, the loop is not working. I also tried a blade for looping but have the same problem.
在我的 Laravel 项目中，我有一个 BusController.php 文件，我需要在其中运行 for() 循环。但是，循环不起作用。我也试过一个刀片来循环，但有同样的问题。
BusController.php
总线控制器.php
<?php
namespace App\Http\Controllers;
use Illuminate\Http\Request;
use DB;
use App\Bus;
use App\Bus_type;
use App\Company;
use App\Http\Requests;
class BusController extends Controller
{
public function index()
{
$buses = Bus::all();
$bus_types = Bus_type::all();
$companies = Company::all();
return view('admin.adding_bus', compact('buses', 'bus_types', 'companies'));
}
public function store(Request $request)
{
$bus = new Bus;
$bus->company_name = $request->company_name;
$bus->bus_type = $request->bus_type;
$bus->bus_number = $request->bus_number;
$bus->no_of_rows = $request->no_of_rows;
$bus->no_of_columns = $request->no_of_columns;
$seats = "";
for ($i = 1; $i <= ($request->no_of_rows * $request->no_of_columns); $i++) {
$seats = $seats . "b";
}
$bus->seats = $seats;
$bus->save();
$buses = Bus::all();
$bus_types = Bus_type::all();
$companies = Company::all();
return view('admin.adding_bus', compact('buses', 'bus_types', 'companies'));
}
}
回答by niko
Make sure you have validated the data you received from the Request. Because if you don't the loop will be fail since the loop conditionwill always be false.
And to test it, here's what I do:
确保您已验证从Request. 因为如果你不这样做，循环就会失败，因为loop condition永远是假的。为了测试它，这就是我所做的：
$seats = "";
$num_cols = 2;
$num_rows = ''; // assume you don't validate the request, so this can receive empty string too
// $num_rows = 0; // will output the same as above
for($i = 1;$i<=($num_cols * $num_rows);$i++)
{
$seats = $seats."b";
}
var_dump($seats);
Output:
输出：
string(0) ""
And here it is working one:
在这里它正在工作：
$seats = "";
$num_cols = 2;
$num_rows = 20; // correctly validated as integer and must be more than 0 because you're doing multiplication here in the following loop
for($i = 1;$i<=($num_cols * $num_rows);$i++)
{
$seats = $seats."b";
}
var_dump($seats);
Output:
输出：
string(40) "bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb"
