Resource.swift
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//
// Resource.swift
// Kingfisher
//
// Created by Wei Wang on 15/4/6.
//
// Copyright (c) 2018 Wei Wang <onevcat@gmail.com>
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.
import Foundation
/// `Resource` protocol defines how to download and cache a resource from network.
public protocol Resource {
/// The key used in cache.
var cacheKey: String { get }
/// The target image URL.
var downloadURL: URL { get }
}
/**
ImageResource is a simple combination of `downloadURL` and `cacheKey`.
When passed to image view set methods, Kingfisher will try to download the target
image from the `downloadURL`, and then store it with the `cacheKey` as the key in cache.
*/
public struct ImageResource: Resource {
/// The key used in cache.
public let cacheKey: String
/// The target image URL.
public let downloadURL: URL
/**
Create a resource.
- parameter downloadURL: The target image URL.
- parameter cacheKey: The cache key. If `nil`, Kingfisher will use the `absoluteString` of `downloadURL` as the key.
- returns: A resource.
*/
public init(downloadURL: URL, cacheKey: String? = nil) {
self.downloadURL = downloadURL
self.cacheKey = cacheKey ?? downloadURL.absoluteString
}
}
/**
URL conforms to `Resource` in Kingfisher.
The `absoluteString` of this URL is used as `cacheKey`. And the URL itself will be used as `downloadURL`.
If you need customize the url and/or cache key, use `ImageResource` instead.
*/
extension URL: Resource {
public var cacheKey: String { return absoluteString }
public var downloadURL: URL { return self }
}