oobject102306.htm

UML基础(好)

                  </font><font color="#000000">以及訊息</font><font face="Comic Sans MS"><font color="#000000">(Message)</font></p>
                  <li>
                    <p class="MsoNormal" style="MARGIN: 0pt 0cm 6pt; TEXT-INDENT: 24pt"></font><font color="#000000">繼承</font><font face="Comic Sans MS" color="#000000">(Inheritance)</font><font color="#000000">。</font></p>
                <li>
                  <p class="MsoNormal" style="MARGIN: 0pt 0cm 6pt; TEXT-INDENT: 24pt"><font color="#000000">封裝</font><font face="Comic Sans MS" color="#000000">(Encapsulation)</font><font color="#000000">。</font></p>
                <li>
                  <p class="MsoNormal" style="MARGIN: 0pt 0cm 6pt; TEXT-INDENT: 24pt"><font color="#000000">動態連結</font><font face="Comic Sans MS" color="#000000">(Dynamic 
                  Binding)</font><font color="#000000">。</font></p>
                </li>
              </ol>
              <p class="MsoNormal" style="MARGIN: 6pt 0cm 12pt; TEXT-INDENT: 24pt"><font color="#000000">而其中繼承、封裝、動態連結則又是物件導向中，最重要也具盛名的特性，所以很多人都據此來評斷，哪種語言或工具是不是支援 
              </font><font face="Comic Sans MS" color="#000000">OO</font><font color="#000000">，特別是我們可以在一些論壇之中，常常可以見到諸如這樣的評語：『</font><font face="Comic Sans MS" color="#000000">VB 
              </font><font color="#000000">不支援類別（</font><font face="Comic Sans MS" color="#000000">Class</font><font color="#000000">）的繼承概念，同時也不支援資訊封裝的方法，所以 
              </font><font face="Comic Sans MS" color="#000000">VB </font><font color="#000000">不是一個 
              </font><font face="Comic Sans MS" color="#000000">OO </font><font color="#000000">程式語言』、『</font><font face="Comic Sans MS" color="#000000">Java 
              </font><font color="#000000">由於不支援指標型態，因此更能徹底封裝類別的資訊，跟 
              </font><font face="Comic Sans MS" color="#000000">C++ </font><font color="#000000">比較起來更能貼近 
              </font><font face="Comic Sans MS" color="#000000">OO </font><font color="#000000">的精神』然而對於這些評語，筆者姑且不討論他們之間的對錯，只是覺得發表這些評論的人，把上述 
              </font><font face="Comic Sans MS" color="#000000">OO </font><font color="#000000">的特性，當作是個『定理』來遵從了，所以才造成論壇中的烽煙四起、口水肆溢的現象出現。其實，事實上在各家程式語言之中，對於 
              </font><font face="Comic Sans MS" color="#000000">OO </font><font color="#000000">支援的程度都不一致，特別是連號稱 
              </font><font face="Comic Sans MS" color="#000000">OO </font><font color="#000000">的先驅 
              </font><font face="Comic Sans MS" color="#000000">C++ </font><font color="#000000">都是如此，所以如果我們硬是以某一種語言作為標準，來評斷其他語言作法上並不公平。因此筆者根據 
              </font><font face="Comic Sans MS" color="#000000">Brad Cox </font><font color="#000000">所公布的 
              </font><font face="Comic Sans MS" color="#000000">OO </font><font color="#000000">特性，在此大膽的進行一項假設，『<b>凡是支援繼承、封裝、動態連結的程式語言或工具，我們可以說它們是支援 
              </b></font><b><font face="Comic Sans MS" color="#000000">OO </font><font color="#000000">的，反之則亦然</font></b><font color="#000000">』。現在我們就對這個假設開始進行驗證，不過在此之前我們首先對剛剛所謂的 
              </font><font face="Comic Sans MS" color="#000000">OO </font><font color="#000000">特性進行以下的定義：</font></p>
              <ol>
                <li>
                  <p class="MsoNormal" style="MARGIN: 6pt 0cm 12pt; TEXT-INDENT: 24pt"><font color="#000000">繼承 
                  </font><font face="Comic Sans MS" color="#000000">→ Source </font><font color="#000000">的 
                  </font><font face="Comic Sans MS" color="#000000">Reuse</font><font color="#000000">。</font></p>
                <li>
                  <p class="MsoNormal" style="MARGIN: 6pt 0cm 12pt; TEXT-INDENT: 24pt"><font color="#000000">封裝 
                  </font><font face="Comic Sans MS" color="#000000">→ </font><font color="#000000">保護程式中的資訊，是透過驗證過的程序來存取。</font></p>
                <li>
                  <p class="MsoNormal" style="MARGIN: 6pt 0cm 12pt; TEXT-INDENT: 24pt"><font color="#000000">動態連結 
                  </font><font face="Comic Sans MS" color="#000000">→ </font><font color="#000000">於執行時期決定執行物件的種類與分法。</font></p>
                </li>
              </ol>
              <p class="MsoNormal" style="MARGIN: 6pt 0cm 12pt; TEXT-INDENT: 24pt"><font color="#000000">我們以繼承與封裝為例，並且以素有 
              </font><font color="#000000"><font face="Comic Sans MS">OO </font>之稱的 
              <font face="Comic Sans MS">Delphi</font>，與不支援 <font face="Comic Sans MS">OO 
              </font>的 <font face="Comic Sans MS">VB </font>兩種工具，來逐一比對它們之間的差異。</font></p>
              <div style="BORDER-RIGHT: 2px solid; PADDING-RIGHT: 4px; BORDER-TOP: 2px solid; PADDING-LEFT: 4px; PADDING-BOTTOM: 1px; BORDER-LEFT: 2px solid; PADDING-TOP: 1px; BORDER-BOTTOM: 2px solid; BACKGROUND-COLOR: #ffccff">
                <p class="MsoNormal" style="MARGIN: 0px 0cm 0px 0pt; TEXT-INDENT: 24pt"><span lang="EN-US"><font face="Comic Sans MS"><font color="#000000">&nbsp;</font></font></span><font color="#000000"><span lang="EN-US" style="FONT-FAMILY: Comic Sans MS">type</span></font></p>
                <p class="MsoNormal" style="MARGIN-TOP: 0px; MARGIN-BOTTOM: 0px; TEXT-INDENT: 27pt"><span lang="EN-US" style="FONT-FAMILY: Comic Sans MS"><font color="#000000">&nbsp; 
                TA = class(TObject)</font></span></p>
                <p class="MsoNormal" style="MARGIN-TOP: 0px; MARGIN-BOTTOM: 0px; TEXT-INDENT: 27pt"><span lang="EN-US" style="FONT-FAMILY: Comic Sans MS"><font color="#000000">&nbsp; 
                public</font></span></p>
                <p class="MsoNormal" style="MARGIN-TOP: 0px; MARGIN-BOTTOM: 0px; TEXT-INDENT: 27pt"><span lang="EN-US" style="FONT-FAMILY: Comic Sans MS"><font color="#000000">&nbsp;&nbsp;&nbsp;&nbsp; 
                procedure SayHello;</font></span></p>
                <p class="MsoNormal" style="MARGIN-TOP: 0px; MARGIN-BOTTOM: 0px; TEXT-INDENT: 27pt"><span lang="EN-US" style="FONT-FAMILY: Comic Sans MS"><font color="#000000">&nbsp; 
                end;</font></span></p>
                <p class="MsoNormal" style="MARGIN-TOP: 0px; MARGIN-BOTTOM: 0px; TEXT-INDENT: 27pt"><span lang="EN-US" style="FONT-FAMILY: Comic Sans MS"><font color="#000000">&nbsp;</font></span></p>
                <p class="MsoNormal" style="MARGIN-TOP: 0px; MARGIN-BOTTOM: 0px; TEXT-INDENT: 27pt"><span lang="EN-US" style="FONT-FAMILY: Comic Sans MS"><font color="#000000">&nbsp; 
                TB = class(TA)</font></span></p>
                <p class="MsoNormal" style="MARGIN-TOP: 0px; MARGIN-BOTTOM: 0px; TEXT-INDENT: 27pt"><span lang="EN-US" style="FONT-FAMILY: Comic Sans MS"><font color="#000000">&nbsp; 
                public</font></span></p>
                <p class="MsoNormal" style="MARGIN-TOP: 0px; MARGIN-BOTTOM: 0px; TEXT-INDENT: 27pt"><span lang="EN-US" style="FONT-FAMILY: Comic Sans MS"><font color="#000000">&nbsp;&nbsp;&nbsp;&nbsp; 
                procedure SayHello;</font></span></p>
                <p class="MsoNormal" style="MARGIN-TOP: 0px; MARGIN-BOTTOM: 0px; TEXT-INDENT: 27pt"><span lang="EN-US" style="FONT-FAMILY: Comic Sans MS"><font color="#000000">&nbsp; 
                end;</font></span></p>
                <p class="MsoNormal" style="MARGIN-TOP: 0px; MARGIN-BOTTOM: 0px; TEXT-INDENT: 27pt"><span lang="EN-US" style="FONT-FAMILY: Comic Sans MS"><font color="#000000">&nbsp;</font></span></p>
                <p class="MsoNormal" style="MARGIN-TOP: 0px; MARGIN-BOTTOM: 0px; TEXT-INDENT: 27pt"><span lang="EN-US" style="FONT-FAMILY: Comic Sans MS"><font color="#000000">procedure 
                TB.SayHello;</font></span></p>
                <p class="MsoNormal" style="MARGIN-TOP: 0px; MARGIN-BOTTOM: 0px; TEXT-INDENT: 27pt"><span lang="EN-US" style="FONT-FAMILY: Comic Sans MS"><font color="#000000">begin</font></span></p>
                <p class="MsoNormal" style="MARGIN-TOP: 0px; MARGIN-BOTTOM: 0px; TEXT-INDENT: 27pt"><span lang="EN-US" style="FONT-FAMILY: Comic Sans MS"><font color="#000000">&nbsp;&nbsp; 
                Inherited;</font></span></p>
                <p class="MsoNormal" style="MARGIN-TOP: 0px; MARGIN-BOTTOM: 0px; TEXT-INDENT: 27pt"><span lang="EN-US" style="FONT-FAMILY: Comic Sans MS"><font color="#000000">&nbsp;&nbsp; 
                ShowMessage('Hello by Class B ...');</font></span></p>
                <p class="MsoNormal" style="MARGIN-TOP: 0px; MARGIN-BOTTOM: 0px; TEXT-INDENT: 27pt"><span lang="EN-US" style="FONT-FAMILY: Comic Sans MS"><font color="#000000">end;</font></span></p>
                <p class="MsoNormal" style="MARGIN-TOP: 0px; MARGIN-BOTTOM: 0px; TEXT-INDENT: 27pt"><span lang="EN-US" style="FONT-FAMILY: Comic Sans MS"><font color="#000000">&nbsp;</font></span></p>
                <p class="MsoNormal" style="MARGIN-TOP: 0px; MARGIN-BOTTOM: 0px; TEXT-INDENT: 27pt"><span lang="EN-US" style="FONT-FAMILY: Comic Sans MS"><font color="#000000">procedure 
                TA.SayHello;</font></span></p>
                <p class="MsoNormal" style="MARGIN-TOP: 0px; MARGIN-BOTTOM: 0px; TEXT-INDENT: 27pt"><span lang="EN-US" style="FONT-FAMILY: Comic Sans MS"><font color="#000000">begin</font></span></p>
                <p class="MsoNormal" style="MARGIN-TOP: 0px; MARGIN-BOTTOM: 0px; TEXT-INDENT: 27pt"><span lang="EN-US" style="FONT-FAMILY: Comic Sans MS"><font color="#000000">&nbsp;&nbsp; 
                ShowMessage('Hello by Class A ...');</font></span></p>
                <p class="MsoNormal" style="MARGIN-TOP: 0px; MARGIN-BOTTOM: 0px; TEXT-INDENT: 27pt"><span lang="EN-US" style="FONT-FAMILY: Comic Sans MS"><font color="#000000">end;</font></span></p>
              </div>
              <p class="MsoNormal" style="MARGIN: 0cm 0cm 0pt"><span lang="EN-US"><font face="Comic Sans MS" color="#000000">&nbsp;</font></span></p>
              <p class="MsoNormal" style="MARGIN: 6pt 0cm 12pt; TEXT-INDENT: 24pt"><font color="#000000">上面的範例是一個簡單繼承的例子，我們可以看出其中的繼承關係，其實只不過是從一個函數再去呼叫另一個函數而已，所以如果單單從這個觀點來看的話，</font><font face="Comic Sans MS" color="#000000">VB 
              </font><font color="#000000">也是可以做的到的。</font></p>
              <div style="BORDER-RIGHT: 2px solid; PADDING-RIGHT: 4px; BORDER-TOP: 2px solid; PADDING-LEFT: 4px; PADDING-BOTTOM: 1px; BORDER-LEFT: 2px solid; PADDING-TOP: 1px; BORDER-BOTTOM: 2px solid; BACKGROUND-COLOR: #ffccff">
                <p class="MsoNormal" style="MARGIN: 0px 0cm 0px 0pt; TEXT-INDENT: 24pt"><span lang="EN-US"><font face="Comic Sans MS"><font color="#000000">&nbsp;</font></font></span><font color="#000000"><span lang="EN-US" style="FONT-FAMILY: Comic Sans MS">TC 
                = class(TObjct)</span></font></p>
                <p class="MsoNormal" style="MARGIN-TOP: 0px; MARGIN-BOTTOM: 0px; TEXT-INDENT: 27pt"><span lang="EN-US" style="FONT-FAMILY: Comic Sans MS"><font color="#000000">&nbsp; 
                private</font></span></p>
                <p class="MsoNormal" style="MARGIN-TOP: 0px; MARGIN-BOTTOM: 0px; TEXT-INDENT: 27pt"><span lang="EN-US" style="FONT-FAMILY: Comic Sans MS"><font color="#000000">&nbsp;&nbsp;&nbsp; 
                FCaption: String;</font></span></p>
                <p class="MsoNormal" style="MARGIN-TOP: 0px; MARGIN-BOTTOM: 0px; TEXT-INDENT: 27pt"><span lang="EN-US" style="FONT-FAMILY: Comic Sans MS"><font color="#000000">&nbsp;&nbsp;&nbsp; 
                function GetCaption: String;</font></span></p>
                <p class="MsoNormal" style="MARGIN-TOP: 0px; MARGIN-BOTTOM: 0px; TEXT-INDENT: 27pt"><span lang="EN-US" style="FONT-FAMILY: Comic Sans MS"><font color="#000000">&nbsp;&nbsp;&nbsp; 
                procedure SetCaption(const Value: String);</font></span></p>
                <p class="MsoNormal" style="MARGIN-TOP: 0px; MARGIN-BOTTOM: 0px; TEXT-INDENT: 27pt"><span lang="EN-US" style="FONT-FAMILY: Comic Sans MS"><font color="#000000">&nbsp; 
                public</font></span></p>
                <p class="MsoNormal" style="MARGIN-TOP: 0px; MARGIN-BOTTOM: 0px; TEXT-INDENT: 27pt"><span lang="EN-US" style="FONT-FAMILY: Comic Sans MS"><font color="#000000">&nbsp;&nbsp;&nbsp; 
                property Caption: String read GetCaption write SetCaption;</font></span></p>
                <p class="MsoNormal" style="MARGIN-TOP: 0px; MARGIN-BOTTOM: 0px; TEXT-INDENT: 27pt"><span lang="EN-US" style="FONT-FAMILY: Comic Sans MS"><font color="#000000">&nbsp; 
                end;</font></span></p>
              </div>
              <p class="MsoNormal" style="MARGIN: 6pt 0cm 12pt; TEXT-INDENT: 24pt"><font color="#000000">　</font></p>
              <p class="MsoNormal" style="MARGIN: 6pt 0cm 12pt; TEXT-INDENT: 24pt"><font color="#000000">上面是一個資訊封裝的例子，其中屬性 
              </font><font face="Comic Sans MS" color="#000000">Caption </font><font color="#000000">必須透過 
              </font><font face="Comic Sans MS" color="#000000">GetCaption </font><font color="#000000">與 
              </font><font face="Comic Sans MS" color="#000000">SetCaption </font><font color="#000000">這兩個方法才能存取得到，目的在於保護