Matlab迭代器模式

迭代器（Iterator）模式，又叫做游標（Cursor）模式。提供一種方法訪問一個容器（container）或者聚集（Aggregator）對象中各個元素，而又不需暴露該對象的內部細節。在採用不同的方式迭代時，只需要替換相應Iterator類即可。本文采用Matlab語言實現對元胞數組和string數組的遍歷。

Aggregator.m

classdef Aggregator < handle
    methods(Abstract)
        iterObj = createIterator(~);
    end
end

CellAggregator.m

classdef CellAggregator < Aggregator
    properties
        cell
    end   
    methods
        function obj = CellAggregator(cell)
            obj.cell = cell;
        end       
        function iterObj = createIterator(obj)
            iterObj = CellIterator(obj);
        end
    end
end

StringAggregator.m

classdef StringAggregator < Aggregator
    properties
        string_arr
    end   
    methods
        function obj = StringAggregator(string_arr)
            obj.string_arr = string_arr;
        end       
        function iterObj = createIterator(obj)
            iterObj = StringIterator(obj);
        end
    end
end

Iterator.m

classdef Iterator < handle
    methods(Abstract)
        hasNext(~);
        next(~);
    end
end

CellIterator.m

classdef CellIterator < Iterator
    properties
        index = 1;
        aggHandle;
    end
    methods
        function obj = CellIterator(agg)
            obj.aggHandle = agg;
        end
        function res = hasNext(obj)
            if(obj.index <= length(obj.aggHandle.cell))
                res = true;
            else
                res = false;
            end
        end
        function ele = next(obj)
            if(obj.hasNext())
                ele = obj.aggHandle.cell{obj.index};
                obj.index = obj.index + 1;
            else
                ele = [];
            end
        end
    end
end

StringIterator.m

classdef StringIterator < Iterator
    properties
        index = 1;
        aggHandle;
    end
    methods
        function obj = StringIterator(agg)
            obj.aggHandle = agg;
        end
        function res = hasNext(obj)
            if(obj.index <= obj.aggHandle.string_arr.length)
                res = true;
            else
                res = false;
            end
        end
        function ele = next(obj)
            if(obj.hasNext())
                ele = obj.aggHandle.string_arr(obj.index);
                obj.index = obj.index + 1;
            else
                ele = string.empty();
            end
        end
    end
end

　測試代碼：

cell = CellAggregator({'matlab','cell','iter'});
iterObj = cell.createIterator();
while iterObj.hasNext()
    disp(iterObj.next());
end
 
str_arr = StringAggregator(["matlab","string","iter"]);
iterObj = str_arr.createIterator();
while iterObj.hasNext()
    disp(iterObj.next());
end