測試代碼：
protocol TheProtocol {
func method1()
func method3()
}
extension TheProtocol {
func method1() {
print("Called method1 from TheProtocol")
}
func method2() {
print("Called method2 from TheProtocol")
}
func method3() {
print("Called method3 from TheProtocol")
}
}
struct Struct1: TheProtocol {
func method1() {
print("called method1 from Struct1")
}
func method2() {
print("called method2 from Struct1")
}
}
let s1 = Struct1()
s1.method1()
s1.method2()
s1.method3()
print("\n-----------------\n")
let s2:TheProtocol = Struct1()
s2.method1()
s2.method2() // 如果在 extension TheProtocol 未實(shí)現(xiàn)該方法百新，編譯報(bào)錯(cuò)
s1.method3()
print("\n-----------------\n")
結(jié)論：
image
參考：
http://www.reibang.com/p/3b3219fb8ada
https://medium.com/ios-os-x-development/swift-protocol-extension-method-dispatch-6a6bf270ba94
