组合模式能够使容器与内容具有一致性,创造出递归结构,将对象组合成树形结构以表示“部分-整体”的层次结构.
组合模式.pngLeaf(树叶):表示叶节点对象,叶子节点没有子节点,不能放入其他对象.
Composite(复合物): 可以存储Leaf对象,也可以存储Composite对象,相当于容器.
Component : 组合中的对象声明接口, 定义Leaf与Compostite的公共行为接口.
现实生活中最符合组合模式结构的莫过于文件系统,文件类似于Leaf,文件夹类似于Composite.
核心代码:
class Entry {
var parent:Directory?
var name:String?
convenience init(name:String,parent:Directory?) {
self.init()
self.name = name
self.parent = parent
}
func addEntry(entry:Entry) {}
func deleteEntry(entry:Entry) {}
func printnEntry() {}
func printEntry(prefix:String) {}
}
class File:Entry {
override func printnEntry() {
print("目录:\(String(describing: self.parent!.name!))/\(String(describing: self.name!))")
}
override func printEntry(prefix: String) {
print("目录:\(prefix)/\(String(describing: self.parent!.name!))/\(String(describing: self.name!))")
}
}
class Directory: Entry {
var files = [File]()
var dirs = [Directory]()
override func addEntry(entry: Entry) {
if entry is File {
files.append(entry as! File)
} else {
dirs.append(entry as! Directory)
}
}
override func deleteEntry(entry:Entry) {
if entry is File {
for i in 0..<files.count {
if entry.name == files[i].name {
files.remove(at: i)
}
}
} else {
for i in 0..<dirs.count {
if entry.name == dirs[i].name {
dirs.remove(at: i)
}
}
}
}
override func printnEntry() {
for file in files {
file.printnEntry()
}
for dir in dirs {
for file in dir.files {
file.printEntry(prefix: self.name!)
}
}
}
}
测试代码:
let rootDir:Directory = Directory(name: "root", parent: nil)
let file:File = File(name: "study.html", parent: rootDir)
let file2:File = File(name: "readme.txt", parent: rootDir)
let studyDir:Directory = Directory(name: "study", parent: rootDir)
let file3:File = File(name: "composite.swift", parent: studyDir)
let file4:File = File(name: "study.project", parent: studyDir)
rootDir.addEntry(entry: file)
rootDir.addEntry(entry: file2)
rootDir.addEntry(entry: studyDir)
studyDir.addEntry(entry: file3)
studyDir.addEntry(entry: file4)
rootDir.printnEntry()
print("FlyElephant---删除文件夹")
rootDir.deleteEntry(entry:studyDir)
rootDir.printnEntry()
print("FlyElephant---删除文件")
rootDir.deleteEntry(entry:file2)
rootDir.printnEntry()
FlyElephant.png
组合模式定义由 Leaf 对象和 Composite 对象组成的类结构,调用简单,添加或删除子部件变得很容易.
网友评论