MATLAB言語で学ぶ「Java言語で学ぶデザインパターン入門」ノート #1 Iterator

概要

Iterator パターンは、複数の要素を順番に指し示し、全体をスキャンしていく、デザインパターンの一つである。

ソースコード

Aggregate.m

classdef (Abstract) Aggregate < handle
    methods (Abstract)
        out = iterator(obj)
    end
end

Iterator.m

classdef (Abstract) Iterator < handle
    methods (Abstract)
        out = hasNext(obj);
        out = next(obj);
    end
end

Book.m

classdef Book < handle
    properties(Access = private)
        name char {mustBeTextScalar} = ''
    end
    methods (Access = public)
        function obj = Book(name)
            arguments (Input)
                name char {mustBeTextScalar}
            end
            arguments (Output)
                obj (1,1) Book
            end
            obj.name = name;
        end
        function name = getName(obj)
            arguments (Input)
                obj (1,1) Book
            end
            arguments (Output)
                name char {mustBeTextScalar}
            end
            name = obj.name;
        end
    end
end

BookShelf.m

classdef BookShelf < Aggregate
    properties (Access = private)
        books (1,:) Book
        last (1,1) int32 = 1
    end

    methods (Access = public)
        function obj = BookShelf(maxsize)
            arguments (Input)
                maxsize (1,1) double {mustBeInteger}
            end
            arguments (Output)
                obj (1,1) BookShelf
            end
            obj.books = matlab.lang.invalidHandle('Book', 1, maxsize);
        end
        function book = getBookAt(obj, index)
            arguments (Input)
                obj (1,1) BookShelf
                index (1,1) double {mustBeInteger}
            end
            arguments (Output)
                book (1,1) Book
            end
            book = obj.books(index);
        end
        function appendBook(obj, book)
            arguments (Input)
                obj (1,1) BookShelf
                book (1,1) Book
            end
            obj.books(obj.last) = book;
            obj.last = obj.last + 1;
        end
        function last = getLength(obj)
            arguments (Input)
                obj (1,1) BookShelf
            end
            arguments (Output)
                last (1,1) double {mustBeInteger}
            end
            last = obj.last;
        end
        function out = iterator(obj)
            arguments (Input)
                obj (1,1) BookShelf
            end
            arguments (Output)
                out (1,1) BookShelfIterator
            end
            out = BookShelfIterator(obj);
        end
    end
end

BookShelfIterator.m

classdef BookShelfIterator < Iterator
    properties (Access = private)
        bookShelf (1,1) BookShelf = matlab.lang.invalidHandle('BookShelf', 1, 1)
        index int32 = 1
    end

    methods (Access = public)
        function obj = BookShelfIterator(bookShelf)
            arguments (Input)
                bookShelf (1,1) BookShelf
            end
            arguments (Output)
                obj (1,1) BookShelfIterator
            end
            obj.bookShelf = bookShelf;
        end
        function out = hasNext(obj)
            arguments (Input)
                obj (1,1) BookShelfIterator
            end
            arguments (Output)
                out (1,1) logical
            end
            out = obj.index < obj.bookShelf.getLength();
        end
        function out = next(obj)
            arguments (Input)
                obj (1,1) BookShelfIterator
            end
            arguments (Output)
                out (1,1) Book
            end
            out = obj.bookShelf.getBookAt(obj.index);
            obj.index = obj.index + 1;
        end
    end
end

main.m

function main
bookShelf = BookShelf(4);
bookShelf.appendBook(Book('Around the World in 80 Days'));
bookShelf.appendBook(Book('Bible'));
bookShelf.appendBook(Book('Cinderella'));
bookShelf.appendBook(Book('Daddy-Long-Legs'));
it = bookShelf.iterator();
while it.hasNext()
    book = it.next();
    disp(book.getName());
end
end

実行結果

>> main
Around the World in 80 Days
Bible
Cinderella
Daddy-Long-Legs