马丁 R 有正确的答案。但是,当基本 URL 是文件本身时,我遇到了问题。因此,我做了一些调整:
func relativePath(from base: URL) -> String? {
// Ensure that both URLs represent files:
guard self.isFileURL && base.isFileURL else {
return nil
}
//this is the new part, clearly, need to use workBase in lower part
var workBase = base
if workBase.pathExtension != "" {
workBase = workBase.deletingLastPathComponent()
}
// Remove/replace "." and "..", make paths absolute:
let destComponents = self.standardized.resolvingSymlinksInPath().pathComponents
let baseComponents = workBase.standardized.resolvingSymlinksInPath().pathComponents
// Find number of common path components:
var i = 0
while i < destComponents.count &&
i < baseComponents.count &&
destComponents[i] == baseComponents[i] {
i += 1
}
// Build relative path:
var relComponents = Array(repeating: "..", count: baseComponents.count - i)
relComponents.append(contentsOf: destComponents[i...])
return relComponents.joined(separator: "/")
}
我的测试用例有点扩展。案例 4 是我进行这个小改动的触发因素。
func testRelativePath() {
// This is an example of a functional test case.
// Use XCTAssert and related functions to verify your tests produce the correct results.
func test(_ p1: String, _ p2: String,_ result: String,_ nr: Int) {
let u1 = URL(fileURLWithPath: p1)
let u2 = URL(fileURLWithPath: p2)
let r = u1.relativePath(from: u2)!
XCTAssert( r == result,"\(nr): '\(r)' != '\(result)'")
}
test("/usr/X11/agent/47.gz", "/usr/X11","agent/47.gz", 1)
test("/usr/share/man/meltdown.1", "/usr/share/cups", "../man/meltdown.1",2 )
test("/var/logs/x/y/z/log.txt", "/var/logs", "x/y/z/log.txt",3)
test("/usr/embedded.jpg", "/usr/main.html", "embedded.jpg",4)
test("/usr/embedded.jpg", "/usr", "embedded.jpg",5)
test("~/Downloads/resources", "~/", "Downloads/resources",6)
test("~/Downloads/embedded.jpg", "~/Downloads/main.html", "embedded.jpg",7)
test("/private/var/logs/x/y/z/log.txt", "/var/logs", "x/y/z/log.txt",8)
}