php中的方法链

Question

I have the following class

class FormValidator{

    public function __construct() {}

    public function __destruct(){}

    private $value;

    public function Value($value){
        $this->value = trim($value);
        return $this;
    }

    public function Required(){
        if(empty($this->value)){
           return false;
        }
        else{
            return $this;
        }
    }

    public function MinLength($length){
        $len = strlen($this->value);
        if($len < $length){
           return false;
        }
        else{
            return $this;
        }
    }
}

In my php code, I'm calling -

 $validator = new FormValidator();
 $result = $validator->Value("")->Required()->MinLength(5)->SomeOtherMethod();

The above line gives the error Call to a member function MinLength() on a non-object ...

UPDATE: I require to stop to call MinLength() if Required() returns false.

How can I make my statement functioning?

Answer 1

You should make use of exceptions instead, which would handle errors while the methods themselves would always return the current instance.

This becomes:

<?php
class FormValidationException extends \Exception 
{
}

class FormValidator
{
  private $value;

  public function Value($value): self
  {
    $this->value = trim($value);
    return $this;
  }

  /**
   * @return $this
   * @throws FormValidationException
   */
  public function Required(): self
  {
    if (empty($this->value)) {
      throw new \FormValidationException('Value is required.');
    }
    return $this;
  }

  /**
   * @param int $length
   * @return $this
   * @throws FormValidationException
   */
  public function MinLength(int $length): self
  {
    $len = strlen($this->value);
    if ($len < $length) {
      throw new \FormValidationException("Value should be at least {$length} characters long.");
    }
    return $this;
  }
}

Usage:

$validator = new FormValidator();
try {
  $result = $validator->Value("lodddl")->Required()->MinLength(5);
} catch (\FormValidationException $e) {
  echo 'Error: ', $e->getMessage();
}

Demo: https://3v4l.org/OFcPV

Edit : since OP is using PHP 5.2 (sadly), here's a version for it, removing \\ s before root namespace, return type declarations and argument types.

Demo for PHP 5.2: https://3v4l.org/cagWS

Answer 2

cause method Required() returns false not Class object :

    if(empty($this->value)){
        return false;
    }

You must change your code to.

$result = $validator->Value("");
if($result->Required()){ // if is not false do 
   $result->MinLength(5)->SomeOtherMethod();
}else{
    // do anything if value is empty.
}

Answer 3

Instead of working with Exceptions (the solution of @Jeto), you can also work with an array holding all errors. A benefit of this solution is that you'll get multiple errors in one run, instead of breaking at the first error.

<?php
class FormValidator
{
  private $value;

  private $_errors = array();

  public function Value($value)
  {
    $this->value = trim($value);
    return $this;
  }

  /**
   * @return $this
   */
  public function Required()
  {
    if (empty($this->value)) {
      $this->_errors[] = 'Value is required';
    }
    return $this;
  }

  /**
   * @param int $length
   * @return $this
   */
  public function MinLength($length)
  {
    $len = strlen($this->value);
    if ($len < $length) {
      $this->_errors[] = "Value should be at least {$length} characters long.";
    }
    return $this;
  }

  public function hasErrors(){
    return (count($this->_errors) > 0);
  }

  public function getErrors(){
      return $this->_errors;
  }
}

$validator = new FormValidator();
$validator->Value("1234")->Required()->MinLength(5);
if($validator->hasErrors()){
    echo implode('<br>',$validator->getErrors());
}

Example here

Answer 4

In the following methods you are calling to a method on a boolean value.

Required();

MinLength();

In order to solve this problem in the MinLength method:

if($len < $length){

    // As a flag
    $this->failed = true;

    return $this;
}

and the SomeOtherMethod():

public function SomeOtherMethod() {
    if (! $this->failed) {
        // do something...
    } else {
        // do nothing...
    }
}

Do the same for the Requied() method

Answer 5

I have the following class

class FormValidator{

    public function __construct() {}

    public function __destruct(){}

    private $value;

    public function Value($value){
        $this->value = trim($value);
        return $this;
    }

    public function Required(){
        if(empty($this->value)){
           return false;
        }
        else{
            return $this;
        }
    }

    public function MinLength($length){
        $len = strlen($this->value);
        if($len < $length){
           return false;
        }
        else{
            return $this;
        }
    }
}

In my php code, I'm calling -

 $validator = new FormValidator();
 $result = $validator->Value("")->Required()->MinLength(5)->SomeOtherMethod();

The above line gives the error Call to a member function MinLength() on a non-object ...

UPDATE: I require to stop to call MinLength() if Required() returns false.

How can I make my statement functioning?