PHP - 使用大量参数和默认值初始化对象的最佳方法

php idioms class constructor instantiation

2022-08-30 14:38:38

我正在设计一个类，该类定义了一个高度复杂的对象，其中包含大量（50 +）大部分可选参数，其中许多参数具有默认值（例如：）。我正在尝试确定设置构造函数和实例/类变量的最佳方法，以便能够：$type = 'foo'; $width = '300'; $interactive = false;

使类易于使用
使自动记录类变得容易（即：使用phpDocumentor）
优雅地编码

鉴于上述情况，我不想给构造函数传递大量的参数。我将向它传递一个包含初始化值的哈希值，例如：$foo = new Foo(array('type'=>'bar', 'width'=>300, 'interactive'=>false));

在编程类方面，我仍然觉得我宁愿...

class Foo {
    private $_type = 'default_type';
    private $_width = 100;
    private $_interactive = true;

    ...
}

...因为我相信这将促进文档生成（你会得到类属性的列表，这让API用户知道他们必须使用哪些“选项”），并且它“感觉”是正确的方法。

但是，然后你遇到了将构造函数中的传入参数映射到类变量的问题，并且在不利用符号表的情况下，你进入了一种“蛮力”方法，这对我来说违背了目的（尽管我对其他意见持开放态度）。例如：

function __construct($args){
    if(isset($args['type'])) $_type = $args['type']; // yuck!
}

我考虑过创建一个单个类变量，它本身就是一个关联数组。初始化这将非常容易，例如：

private $_instance_params = array(
    'type' => 'default_type',
    'width' => 100,
    'interactive' => true
);

function __construct($args){
    foreach($args as $key=>$value){
        $_instance_params[$key] = $value;
    }
}

但这似乎我没有利用私有类变量等本机功能，而且感觉文档生成不适用于这种方法。

感谢您阅读本文;我在这里可能会问很多，但我是PHP的新手，我真的只是在寻找习惯用语/优雅的方法来做到这一点。您的最佳实践是什么？

附录（有关此特定类的详细信息）

这个类很可能试图做太多的事情，但它是一个用于创建和处理表单的旧Perl库的移植。可能有一种方法可以划分配置选项以利用继承和多态性，但实际上可能会适得其反。

根据要求，以下是一些参数（Perl代码）的部分列表。您应该看到这些不能很好地映射到子类。

该类当然具有许多这些属性的 getter 和 setter，因此用户可以覆盖它们;这篇文章的目标（以及原始代码做得很好的事情）是提供一种紧凑的方式来实例化这些Form对象，这些对象已经设置了必需的参数。它实际上使代码非常可读。

# Form Behaviour Parameters
        # --------------------------
        $self->{id}; # the id and the name of the <form> tag
        $self->{name} = "webform"; # legacy - replaced by {id}
        $self->{user_id} = $global->{user_id}; # used to make sure that all links have the user id encoded in them. Usually this gets returned as the {'i'} user input parameter
        $self->{no_form}; # if set, the <form> tag will be omitted
        $self->{readonly}; # if set, the entire form will be read-only
        $self->{autosave} = ''; # when set to true, un-focusing a field causes the field data to be saved immediately
        $self->{scrubbed}; # if set to "true" or non-null, places a "changed" radio button on far right of row-per-record forms that indicates that a record has been edited. Used to allow users to edit multiple records at the same time and save the results all at once. Very cool.
        $self->{add_rowid}; # if set, each row in a form will have a hidden "rowid" input field with the row_id of that record (used primarily for scrubbable records). If the 'scrubbed' parameter is set, this parameter is also automatically set. Note that for this to work, the SELECT statement must pull out a unique row id. 
        $self->{row_id_prefix} = "row_"; # each row gets a unique id of the form id="row_##" where ## corresponds to the record's rowid. In the case of multiple forms, if we need to identify a specific row, we can change the "row_" prefix to something unique. By default it's "row_"

        $self->{validate_form}; # parses user_input and validates required fields and the like on a form
        $self->{target}; # adds a target window to the form tag if specified
        $self->{focus_on_field}; # if supplied, this will add a <script> tag at the end of the form that will set the focus on the named field once the form loads.
        $self->{on_submit}; # adds the onSubmit event handler to the form tag if supplied
        $self->{ctrl_s_button_name}; # if supplied with the name of the savebutton, this will add an onKeypress handler to process CTRL-S as a way of saving the form

        # Form Paging Parameters
        # ----------------------
        $self->{max_rows_per_page}; # when displaying a complete form using printForm() method, determines the number of rows shown on screen at a time. If this is blank or undef, then all rows in the query are shown and no header/footer is produced.
        $self->{max_pages_in_nav} = 7; # when displaying the navbar above and below list forms, determines how many page links are shown. Should be an odd number
        $self->{current_offset}; # the current page that we're displaying
        $self->{total_records}; # the number of records returned by the query
        $self->{hide_max_rows_selector} = ""; # hide the <select> tag allowing users to choose the max_rows_per_page
        $self->{force_selected_row} = ""; # if this is set, calls to showPage() will also clear the rowid hidden field on the form, forcing the first record to be displayed if none were selected
        $self->{paging_style} = "normal"; # Options: "compact"

当然，我们可以允许自己卷入一场关于编程风格的更冗长的辩论。但我希望避免它，为了所有参与者的理智！这里（再次是Perl代码）是一个使用一组相当多的参数实例化此对象的示例。

my $form = new Valz::Webform (
            id                      => "dbForm",
            form_name               => "user_mailbox_recip_list_students",
            user_input              => \%params,
            user_id                 => $params{i},
            no_form                 => "no_form",
            selectable              => "checkbox",
            selectable_row_prefix   => "student",
            selected_row            => join (",", getRecipientIDsByType('student')),
            this_page               => $params{c},
            paging_style            => "compact",
            hide_max_rows_selector  => 'true',
            max_pages_in_nav        => 5
        );

答案 1

我可以想到两种方法来做到这一点。如果要保留实例变量，只需循环访问传递给构造函数的数组并动态设置实例变量：

    <?php

    class Foo {
        private $_type = 'default_type';
        private $_width = 100;
        private $_interactive = true;

        function __construct($args){
            foreach($args as $key => $val) {
                $name = '_' . $key;
                if(isset($this->{$name})) {
                    $this->{$name} = $val;
                }
            }
        }
    }

    ?>

使用数组方法时，您实际上不必放弃文档。只需在类正文中使用@property注释：

<?php

/**
 * @property string $type
 * @property integer $width
 * @property boolean $interactive
 */
class Foo {
    private $_instance_params = array(
        'type' => 'default_type',
        'width' => 100,
        'interactive' => true
    );

    function __construct($args){
        $this->_instance_params = array_merge_recursive($this->_instance_params, $args);
    }

    public function __get($name)
    {
        return $this->_instance_params[$name];
    }

    public function __set($name, $value)
    {
        $this->_instance_params[$name] = $value;
    }
}

?>

也就是说，具有50个成员变量的类要么仅用于配置（可以拆分），要么只是做得太多，您可能需要考虑重构它。

答案 2

另一种方法是使用对象实例化类，仅充当选项容器：FooOptions

<?php
class Foo 
{
    /*
     * @var FooOptions
     */
    private $_options;

    public function __construct(FooOptions $options) 
    {
        $this->_options = $options;
    }
}


class FooOptions
{
    private $_type = 'default_type';
    private $_width = 100;
    private $_interactive = true;

    public function setType($type);
    public function getType();

    public function setWidth($width);
    public function getWidth();

    // ...
}

您的选项已得到很好的记录，并且您可以轻松设置/检索它们。这甚至有助于您的测试，因为您可以创建和设置不同的选项对象。

我不记得这个模式的确切名称，但我认为它是Builder或Option模式。