lecture9_the_state_pattern.pdf - CSC3380 Object Oriented Design Lecture 9 The state pattern The Quiz Quiz Answer Writing Code(The lesson of the

lecture9_the_state_pattern.pdf - CSC3380 Object Oriented...

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CSC3380 Object Oriented Design Lecture 9: The state pattern
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The Quiz
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Quiz Answer
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Writing Code (The lesson of the CoolCam™)
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The Project Grade is multiplied by the participation score A 0% participation score means a 0% project grade A 50% participation score and a 80% project grade means a personal score of 40%.
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This class The state pattern
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Motivating example Suppose we’re developing a video game… We have the following “states”: Main menu Character Select In-game Each state has dramatically different behavior! (Also applies to simulations and many servers)
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The basics: Every game and simulation has a main loop The main loop runs multiple times per second to maintain the game: Check for button presses Update the interface Process animations Move objects / process physics etc.
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Structured Approach Giant switch-case or if-then statement inside of main loop: void update() { if ( currentState == MAIN_MENU ) { drawMainMenu(); checkMenuButtonClicked(); } else if ( currentState == IN_GAME ) { drawCharacters(); drawInterface(); getCurrentMove(); } }
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What’s wrong? What’s wrong with having a single switch-case to perform updates?
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Issues The states should be totally independent, but they exist in the same function.
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  • Spring '09
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