KnockoutJS:RangeError:超出最大调用堆栈大小;

Question

注册产品时,用户可以自定义它的URL!当用户输入Tipo de produto,Nome或者Link,网站将显示该产品的URL如何

完整网址:http: //i.stack.imgur.com/jZg7G.png

请注意,"Tipo de produto"字段也会修改URL !!

为此,我在KnockoutJS中创建了一个帮助器

码

KnockoutJS

ko.bindingHandlers.url =
    update: (element, valueAccessor, allBindingsAccessor, viewModel) ->
        link = ko.utils.unwrapObservable(valueAccessor())
        if link
            link = link.toLowerCase().trim().replaceAll(" ", "-")
            link = encodeURI(link)
        else
            link = ""
        valueAccessor()(link)
        $(element).nextAll(".link-exibicao").text(link).effect("highlight", { color: "#FDBB30" }, 800 )

此帮助程序的唯一目的是生成有效的URL并在span中显示它 .link-exibicao

视图模型

public class ProdutoViewModel
{
    [AdditionalMetadata("data-bind", "event: { change: function(data) { Link(data.Nome());  }}")]
    public string Nome { get; set; }

    [DataType(DataType.Url)]
    [AdditionalMetadata("Prefixo", "Produto/")]
    public string Link { get; set; }

    [Display(Name = "Descrição")]
    [DataType(DataType.MultilineText)]
    public string Descricao { get; set; }

    public int? Ordem { get; set; }
}

AdditionalMetadata将添加具有该名称和值的属性.例如,该属性Name将生成HTML:

<input data-bind="value: Nome, event: { change: function(data) { Link(data.Nome());  }}" id="Nome" name="Nome" type="text" value="">

Url.cshtml

下一步是data-bind="url: Link"在URL类型的所有字段中添加标记:

@model string
@{

    var values = ViewData.ModelMetadata.AdditionalValues;
    object objDatabind;
    string data_bind = "";
    if (values.TryGetValue("data-bind", out objDatabind))
    {
        data_bind = objDatabind.ToString();
    }

    var nomeCampo = Html.IdForModel();

    var objPrefixo = values["Prefixo"];
    string prefixo = objPrefixo.ToString();
    string separador = "/";
    if (!string.IsNullOrWhiteSpace(prefixo))
    {
        if (prefixo.EndsWith("/") || prefixo.EndsWith("#"))
        {
            separador = prefixo[prefixo.Length - 1].ToString();
            prefixo = prefixo.Substring(0, prefixo.Length - 1);
        }   
    }
}

@Html.TextBoxFor(p => Model, new { data_bind = "value: " + nomeCampo + ", url: " + nomeCampo + (string.IsNullOrWhiteSpace(data_bind) ? "" : ", " + data_bind) })
@Request.Url.Host/<span class="link-prefixo">@prefixo</span><span class="link-separador">@separador</span><span class="link-exibicao"></span>

ProdutoViewModel.cshtml

最后,最简单的步骤是构建form =):

<div class="editor-label">
    <label>Tipo de produto</label>
</div>
<div class="editor-field">
    <select data-bind="options: Tipos, optionsText: 'Nome', value: TipoSelecionado, optionsCaption: 'Selecione...'"></select>
</div>

<div class="editor-label">
    @Html.LabelFor(p => p.Nome)
</div>
<div class="editor-field">
    @Html.EditorFor(p => p.Nome)
    @Html.ValidationMessageFor(p => p.Nome)
</div>

<div class="editor-label">
    @Html.LabelFor(p => p.Link)
</div>
<div class="editor-field">
    @Html.EditorFor(p => p.Link)
    @Html.ValidationMessageFor(p => p.Link)
</div>

<div class="editor-label">
    @Html.LabelFor(p => p.Descricao)
</div>
<div class="editor-field">
    @Html.EditorFor(p => p.Descricao)
    @Html.ValidationMessageFor(p => p.Descricao)
</div>

<div class="editor-label">
    @Html.LabelFor(p => p.Ordem)
</div>
<div class="editor-field">
    @Html.EditorFor(p => p.Ordem)
    @Html.ValidationMessageFor(p => p.Ordem)
</div>

问题

每当键入简单的单词如:"我的产品名称"一切都完美无缺!
但是meu prodúto côm açênto会显示如下错误的字样!

Uncaught Error: Unable to parse bindings.
Message: RangeError: Maximum call stack size exceeded;
Bindings value: value: Link, url: Link

Answer 1

在访问值时,bindingHandler会导致递归更新:

link = ko.utils.unwrapObservable(valueAccessor())

然后设置它:

valueAccessor()(link)

如果link最终与其当前值相同,则链将停止(可观察者不通知相同的(===)值).

当你通过时: meu prodúto côm açênto

它成为了: meu-prod%C3%BAto%20c%C3%B4m%20a%C3%A7%C3%AAnto

设置observable时,它会重新触发相同的绑定.所以,它encodeURI再次调用,现在它是双重编码,如:

meu-prod%25C3%25BAto%2520c%25C3%25B4m%2520a%25C3%25A7%25C3%25AAnto

observable再次设置,因为这个值是新的,它会再次触发它(并一次又一次),直到你得到调用堆栈错误.

处理这个问题的一些选择是不回写observable并只使用绑定来编码URL.

否则,一个好的选择是使用a writeable computed observable来拦截对值的写入并在模型中对其进行操作.