使用php和singleton只运行一次该进程

Question

I am reading data from the sheet and want to implement singleton in my process so that I can run read function, one at a time.

I have written a code for the same which calls the class and set a static variable and then call the function to check if it has the class, so if the class is there then don't run the read function.

class DataParser extends config {

   private static $_instance = false;

   public static
   function getInstance() {
     if (self::$_instance == false) {
        print_r("expression");
        self::$_instance = true;
        return self::$_instance;

     }
     return false;
   }

   function __construct($params) {}
}

$dataParser = new DataParser($confData);
$p = DataParser::getInstance();
if ($p) {
 $res = $dataParser - > read();

}

I want to run the read function one at a time, if one read is running then the other read will not run.

Answer 1

A singleton needs to prevent public constructing and cloning. This can simply be achieved by declaring these methods as protected.

To check if read() is currently being executed, you can use a flag $isRunning.

<?php

class DataParser
{
    protected static $instance;

    protected static $isRunning = false;

    protected function __construct()
    {
    }

    protected function __clone()
    {
    }

    public static function getInstance(): DataParser
    {
        if (null === self::$instance) {
            self::$instance = new self();
        }

        return self::$instance;
    }

    public function read(): void
    {
        if (static::$isRunning) {
            throw new RuntimeException('DataParse is already running');
        }

        static::$isRunning = true;

        // Do some reading

        static::$isRunning = false;
    }
}