% add the PATH to retrieve cls and sty beamer styles files \makeatletter \providecommand*{\input@path}{} \edef\input@path{{../../support/beamer/}\input@path}% prepend \makeatother % \documentclass{pharoslides} % \documentclass[aspectratio=169]{pharoslides} % format 16/9 \documentclass[withvideo]{pharoslides} % format 16/9 + incrustation video \graphicspath{{./figures/}{../}{../../support/beamer/imgs/}} %Information to be included in the title page: \title{Hooks and Templates} \subtitle{An application of self-sends are plans for reuse} \author{Damien Cassou, Stéphane Ducasse and Luc Fabresse} \institute{http://stephane.ducasse.free.fr} \date{} \slidesid{W6S05} \begin{document} \frame[plain]{\titlepage} \begin{frame}[fragile] \frametitle{Remember...} \begin{itemize} \item A message send leads to a choice \item A class hierarchy defines the choices \item Code can be reused and refined in subclasses \item Sending a message in a class defines a hook: \begin{itemize} \item i.e., a place where subclasses can inject variations \end{itemize} \end{itemize} \end{frame} \begin{frame}[fragile] \frametitle{The Template Method} \begin{itemize} \item a template method specifies a skeleton \item the skeleton has hooks, i.e., places to be customized \begin{itemize} \item hooks may or may not have a default behavior \end{itemize} \end{itemize} \begin{center} \includegraphics[width=0.85\textwidth]{figures/hookAndTemplate.png}\end{center} \end{frame} \begin{frame}[fragile] \frametitle{printString Template Method} \begin{listing}{} (Delay forSeconds: 10) printString > 'a Delay(10000 msecs)' \end{listing} \begin{listing}{} Object >> printString "Answer a String whose characters are a description of the receiver." ^ self printStringLimitedTo: 50000 Object >> printStringLimitedTo: limit | limitedString | limitedString := String streamContents: [ :s | self printOn: s ] limitedTo: limit. limitedString size < limit ifTrue: [ ^ limitedString ]. ^ limitedString , '...etc...' \end{listing} \end{frame} \begin{frame}[fragile] \frametitle{printOn: Default Hook} \begin{listing}{} Node new > a Node Apple new > an Apple \end{listing} Default behavior: \begin{listing}{} Object >> printOn: aStream "Append to the argument, aStream, a sequence of characters that identifies the receiver." | title | title := self class name. aStream nextPutAll: (title first isVowel ifTrue: [ 'an ' ] ifFalse: [ 'a ' ]); nextPutAll: title \end{listing} \end{frame} \begin{frame}[fragile] \frametitle{printOn: Refinement} \begin{listing}{} (Delay forSeconds: 1) > a Delay(1000 msecs) \end{listing} Reusing and extending default behavior: \begin{listing}{} Delay >> printOn: aStream super printOn: aStream. aStream nextPutAll: '('; print: millisecondDelayDuration; nextPutAll: ' msecs)' \end{listing} \end{frame} \begin{frame}[fragile] \frametitle{printOn: Redefinition} \begin{listing}{} true not > false \end{listing} Redefinition in \code{False}: \begin{listing}{} False >> printOn: aStream aStream nextPutAll: 'false' \end{listing} \end{frame} \begin{frame}[fragile] \frametitle{printOn: Redefinition} \begin{listing}{} 1 to: 100 > (1 to: 100) 1 to: 100 by: 3 > (1 to: 100 by: 3) \end{listing} Redefinition in \code{Interval}: \begin{listing}{} Interval >> printOn: aStream aStream nextPut: $(; print: start; nextPutAll: ' to: '; print: stop. step ~= 1 ifTrue: [ aStream nextPutAll: ' by: '; print: step ]. aStream nextPut: $) \end{listing} \end{frame} \begin{frame}[fragile] \frametitle{Another Template Method: Object Copy} \begin{itemize} \item copying objects is complex: \begin{itemize} \item graph of connected objects \item cycles \item each class may want a different copy strategy \end{itemize} \item simple solution for simple cases: \code{copy}/\code{postCopy} \end{itemize} \end{frame} \begin{frame}[fragile] \frametitle{Object Copy} \begin{listing}{} Object >> copy "Answer another instance just like the receiver. Subclasses typically override postCopy. Copy is a template method in the sense of Design Patterns. So do not override it. Override postCopy instead. Pay attention that normally you should call postCopy of your superclass too." ^ self shallowCopy postCopy \end{listing} \begin{listing}{} Object >> shallowCopy "Answer a copy of the receiver which shares the receiver's instance variables. Subclasses that need to specialize the copy should specialize the postCopy hook method." ... \end{listing} \end{frame} \begin{frame}[fragile] \frametitle{Default hook} \begin{listing}{} Object >> postCopy "I'm a hook method in the sense of Design Patterns TemplateHook/Methods. I'm called by copy. self is a shallow copy, subclasses should copy fields as necessary to complete the full copy" ^ self \end{listing} \end{frame} \begin{frame}[fragile] \frametitle{postCopy: Refinement} \begin{listing}{} Collection subclass: #Bag instanceVariableNames: 'contents' classVariableNames: '' package: 'Collections-Unordered' \end{listing} \begin{listing}{} Bag >> postCopy super postCopy. contents := contents copy \end{listing} \end{frame} \begin{frame}[fragile] \frametitle{postCopy: Deeper copy} \begin{listing}{} Dictionary >> postCopy "Must copy the associations, or later store will affect both the original and the copy" array := array collect: [ :association | association ifNotNil: [ association copy ] ] \end{listing} \end{frame} \begin{frame}[fragile] \frametitle{Conclusion} \begin{itemize} \item Template Method is a very common design pattern \item Sending a message defines a hook \item Sending a message increases potential reuse \end{itemize} \end{frame} % \setlength{\textwidth}{\originaltextwidth} \setbeamertemplate{background canvas}{\insertBorderForHandout} \begin{frame}[plain] \begin{minipage}{\originaltextwidth} \centering \large \vspace{2em} A course by \vspace{1em} \hspace{-20px}\includegraphics[height=32px]{inriaLogo}\hspace{3em}\raisebox{7px}{and}\hspace{3em}\raisebox{-6px}{\includegraphics[height=30px]{logoutop}} \vspace{2em} in collaboration with \vspace{1em} \includegraphics[height=40px]{unisciellogo}\hskip 1.5em% \raisebox{5px}{\includegraphics[height=30px]{unitlogo}}\hskip 2em% \raisebox{8px}{\includegraphics[height=24px]{univLilleLogo}}\hskip 2em% \raisebox{3px}{\includegraphics[height=29px]{logo-IMT}}\hskip 2em% \raisebox{1px}{\includegraphics[height=32px]{minesDouaiLogo}} \vspace{2.5em} \includegraphics[width=50px]{by-nc-nd} \tiny \hskip 0.5em \raisebox{5px}{Inria 2016} \medskip \tiny Except where otherwise noted, this work is licensed under CC BY-NC-ND 3.0 France \url{https://creativecommons.org/licenses/by-nc-nd/3.0/fr/} \end{minipage} \end{frame} \end{document} %%% Local Variables: %%% mode: latex %%% TeX-master: t %%% End: