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Objects and Object-Oriented Programming

Objects and Object-Oriented Programming. CS 110 – Honors Slides by Wanda Dann, Ithaca College. Objects. What is an object ? any thing that can be identified as unique from other things How is an object identified as unique? has a name has properties:

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Objects and Object-Oriented Programming

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  1. Objects and Object-Oriented Programming CS 110 – Honors Slides by Wanda Dann, Ithaca College

  2. Objects • What is an object ? • any thing that can be identified as unique from other things • How is an object identified as unique? • has a name • has properties: • width, height, color, location, age, ss#, id# • has a purpose: • associated actions it can perform • tasks it can carry out

  3. Peter Person Paul Mary Spike Dogs Scottie Fluffy Class • Objects are categorized into classes • Each object is an instance of the class. • All objects in a class have similar propertiesand generally can perform the same tasks.

  4. Objects in a Virtual World • In Alice, each 3-D model is an object • has a unique name • Bunny, Bunny1, Bunny2 • has color(s) • Pink, White, Grey, Black, Blue, …. • has 3 dimensions • height, width, depth

  5. Object Orientation • Each object has 6 degrees of orientation • front, back, left, right, up, down • Orientation is relative to the object itself • Bunny.move(left, 1, …) is a move to the Bunny's left • But, an object is aware of its orientation relative to other objects • Bunny.pointAt(Helicopter)

  6. 3-D Space • An object is located in 3-D space y (0,0,0) x x is left - right y is up - down z is front - back z

  7. Repositioning • Movement of an object changes its position in space. • Some movements are translational • Bunny.move(back, 0.5, …) • Other movements are rotational • Bunny.turn(left, 0.5, …)

  8. Motion Distance • Translational Distance • 1 unit is about 1 meter (relative to the Virtual World dimensions) • Rotational Distance • 1 unit is 1 rotation (360 degrees -- full turn) • Can specify • fractional parts of a unit • 1/2 • 0.5 • multiple units • 2

  9. Instructions • An instruction such as Bunny.move(left, 1, …) is a statement that asks an object to perform an action or carry out a task. • Instructions must follow certain rules of syntax objectName.actionName(argumentList) • Note: • Instructions may have 0, 1, 2, … or more arguments • Some arguments are optional, some are required

  10. Time • Animation takes time -- even on fancy computers! • By default, executing an instruction in Alice takes 1 unit of time (approx. 1 second) • You can specify the amount of time Bunny.move(left, 1, duration = 2) Note: This instruction would slow down the move -- how could you speed it up?

  11. Object Parts • Many objects are made up of parts (we say they are composites) • A part of an object moves • with the entire object, by default • on its own, if given a specific instruction • Bunny.head.leftear.turn(down, 1/8) • Syntax: objectName.partNameList.actionName(argumentList)

  12. Object-Oriented Programming • An Alice program is: • a scene containing • stationary objects -- like props on a stage • active objects -- will move around the scene • a list of instructions that ask the objects to perform tasks in the virtual world • So, an Alice program is object-oriented.

  13. Reading and Lab • See handouts. • Note: Lab exercises and projects require that you show me the code and execution of the programs created. I must "initial" your lab sheet for the exercises and projects or you will not get credit for them!

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