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Switch to slightly higher-level implementation of NavLink (sacrificing some perf for better representation of current idioms)

This commit is contained in:
Steve Sanderson 2018-02-22 14:25:45 +00:00
parent 58ae5dea9a
commit b705ac2c0a
1 changed files with 32 additions and 61 deletions
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93
src/Microsoft.AspNetCore.Blazor.Browser/Routing/NavLink.cs
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@ -5,6 +5,7 @@ using Microsoft.AspNetCore.Blazor.Components;
using Microsoft.AspNetCore.Blazor.RenderTree;
using System;
using System.Collections.Generic;
using System.Linq;
namespace Microsoft.AspNetCore.Blazor.Browser.Routing
{
@ -13,71 +14,57 @@ namespace Microsoft.AspNetCore.Blazor.Browser.Routing
// That's because you'd use NavLink in non-browser scenarios too (e.g., prerendering).
// Can't do this until DI is implemented.
// NOTE: This could be implemented in a more performant way by iterating through
// the ParameterCollection only once (instead of multiple TryGetValue calls), and
// avoiding allocating a dictionary in the case where there are no additional params.
// However the intention here is to get a sense of what more high-level coding patterns
// will exist and what APIs are needed to support them. Later in the project when we
// have more examples of components implemented in pure C# (not Razor) we could change
// this one to the more low-level perf-sensitive implementation.
public class NavLink : IComponent, IDisposable
{
const string CssClassAttributeName = "class";
const string HrefAttributeName = "href";
private RenderHandle _renderHandle;
private bool _isActive;
private RenderFragment _childContent;
private string _cssClass;
private string _href;
private string _hrefAbsolute;
private IDictionary<string, string> _otherAttributes;
private IReadOnlyDictionary<string, object> _allAttributes;
public void Init(RenderHandle renderHandle)
{
_renderHandle = renderHandle;
// We'll consider re-rendering on each location change
UriHelper.OnLocationChanged += OnLocationChanged;
}
public void SetParameters(ParameterCollection parameters)
{
_childContent = null;
_href = null;
_hrefAbsolute = null;
_cssClass = null;
_otherAttributes?.Clear();
foreach (var kvp in parameters)
{
switch (kvp.Name)
{
case RenderTreeBuilder.ChildContent:
_childContent = kvp.Value as RenderFragment;
break;
case CssClassAttributeName:
_cssClass = kvp.Value as string;
break;
case HrefAttributeName:
_href = kvp.Value as string;
_hrefAbsolute = UriHelper.ToAbsoluteUri(_href).AbsoluteUri;
break;
default:
if (kvp.Value != null)
{
if (_otherAttributes == null)
{
_otherAttributes = new Dictionary<string, string>();
}
_otherAttributes.Add(kvp.Name, kvp.Value.ToString());
}
break;
}
}
// Capture the parameters we want to do special things with, plus all as a dictionary
parameters.TryGetValue(RenderTreeBuilder.ChildContent, out _childContent);
parameters.TryGetValue("class", out _cssClass);
parameters.TryGetValue("href", out string href);
_allAttributes = parameters.ToDictionary();
// Update computed state and render
_hrefAbsolute = href == null ? null : UriHelper.ToAbsoluteUri(href).AbsoluteUri;
_isActive = UriHelper.GetAbsoluteUri().Equals(_hrefAbsolute, StringComparison.Ordinal);
_renderHandle.Render(Render);
}
public void Dispose()
{
// To avoid leaking memory, it's important to detach any event handlers
// in Dispose().
UriHelper.OnLocationChanged -= OnLocationChanged;
}
private void OnLocationChanged(object sender, string e)
{
// We could just re-render always, but for this component we know the
// only relevant state change is to the _isActive property.
var shouldBeActiveNow = UriHelper.GetAbsoluteUri().Equals(
_hrefAbsolute,
StringComparison.Ordinal);
@ -85,11 +72,7 @@ namespace Microsoft.AspNetCore.Blazor.Browser.Routing
if (shouldBeActiveNow != _isActive)
{
_isActive = shouldBeActiveNow;
if (_renderHandle.IsInitialized)
{
_renderHandle.Render(Render);
}
_renderHandle.Render(Render);
}
}
@ -97,29 +80,17 @@ namespace Microsoft.AspNetCore.Blazor.Browser.Routing
{
builder.OpenElement(0, "a");
if (!string.IsNullOrEmpty(_href))
// Set "active" class dynamically
builder.AddAttribute(0, "class", CombineWithSpace(_cssClass, _isActive ? "active" : null));
// Pass through all other attributes unchanged
foreach (var kvp in _allAttributes.Where(kvp => kvp.Key != "class"))
{
builder.AddAttribute(0, HrefAttributeName, _href);
builder.AddAttribute(0, kvp.Key, kvp.Value);
}
var combinedClassValue = CombineWithSpace(_cssClass, _isActive ? "active" : null);
if (combinedClassValue != null)
{
builder.AddAttribute(0, CssClassAttributeName, combinedClassValue);
}
if (_otherAttributes != null)
{
foreach (var kvp in _otherAttributes)
{
builder.AddAttribute(0, kvp.Key, kvp.Value);
}
}
if (_childContent != null)
{
builder.AddContent(1, _childContent);
}
// Pass through any child content unchanged
builder.AddContent(1, _childContent);
builder.CloseElement();
}