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Feature UNDERSTAND OBJECT- <strong>ORIENTED</strong> PROGRAMMING Get your head around OOP by using Scratch and Python to create the same programs 66 February 2017 raspberrypi.org/magpi
UNDERSTAND OBJECT-<strong>ORIENTED</strong> PROGRAMMING Feature I n the modern world, almost all of the code you will encounter is created in a style called ‘object-oriented programming’, or OOP for short. If you grew up with OOP, it is the obvious way to create computer programs. In OOP, the code is used to create objects. These represent real-world things: a dog, a chair, or the wheels on a car. Objects contain both the variables that make that thing: a person’s height, age, or a name for example. They also contain the functions that object can perform: a dog can jump, or walk, or run; a wheel can rotate. OOP bundles both the variables and functions together. This style makes it super-easy to cut and paste the code from one program to another. You don’t even need to cut and paste, in fact: you use import statements to get functions and the variables they need. With OOP, you don’t need to create an object for dog you ut find one omeody ee h mde and import it to your program. Importing knowledge t the trt o mot progrm you find unh o import statements. These are used to paste in code which has been created by other people. OOP isn’t perfect. It can be accused of overkill. “The problem with object-oriented languages is they’ve got all this implicit environment that they carry around with them,” says Joe Armstrong, creator of Erlang. “You wanted a banana but what you got was a gorilla holding the banana, and the entire jungle.” There’s also a whole bunch of decorative terminology surrounding OOP. You’ll encounter lots of strange words like ‘encapsulation’ and ‘instantiation’. These make the concept appear much more complicated than it is, and can also be rather oputting to newomer. So OOP is a bit wordy and lends itself to navelgazing. Many makers, hackers, and coders struggle to understand OOP, and indeed you can get a long way without understanding it. Young coders, on the other hand, are increasingly introduced to programming via Scratch. Software like Scratch is included with Raspbian with PIXEL (and Debian with PIXEL) and is designed peifiy to teh tudent tethiy. In Scratch, objects are called ‘Sprites’. They resemble video game characters. The idea is that children brought up on Scratch will inherently feel at home with objects when they migrate to a language like Python. BEYOND PROCEDURE hen o rt tart rogramming, oll egin riting roceral coe n goo olfahione roceral rogramming, o ticall create all or ariale at the tart of a rogram hen o make ome fnction enition thee are lock of reale coe e looke at roceral rogramming in The MagPi ie magpi.cc/2iin6PQ P take all the iling lock of roceral rogramming ariale, fnction, loo, conition t nle them into elfcontaine lock Mot coer create roceral crit that imort oect from mole an ackage So ore ing oect ithot een realiing it P concet are fon in almot all moern rogramming langage, incling Pthon an aa raspberrypi.org/magpi February 2017 67
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THE OFFICIAL RASPBERRY PI MAGAZINE
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Contents Issue 54 February 2017 ras
Page 6 and 7:
News FEATURE RASPBERRY PI ANNOUNCES
Page 8:
News COMPUTE MODULE 3 COMPUTE MODUL
Page 11 and 12:
GAME FOR A LAUGH Pioneers programme
Page 13 and 14:
RASPBERRY PI IN THE HOUSE News RASP
Page 15 and 16: BUILD YOUR OWN MAGIC MIRROR Feature
Page 27 and 28: Pricing Get si issues £30 (UK) £4
Page 29 and 30: MUSEUM IN A BOX Projects Shrunken m
Page 31 and 32: MUSEUM IN A BOX Projects As the ide
Page 33 and 34: SURFACE IMAGER Projects Image court
Page 35: GERO Projects PROGRAM YOUR ROBOT >S
Page 39 and 40: COMMAND LINE Tutorial pi@ he first
Page 41 and 42: COMMAND LINE Tutorial nter pwd agai
Page 43 and 44: COMMAND LINE Tutorial Options ost c
Page 45 and 46: EMPATHYBOT Tutorial >STEP-04 Attach
Page 47 and 48: NIGHT-VISION CAMERA TRAP Tutorial m
Page 49 and 50: NIGHT-VISION CAMERA TRAP Tutorial R
Page 51 and 52: AN INTRODUCTION TO C Tutorial strcp
Page 53 and 54: DRUM LIKE ME Tutorial Sensor Ground
Page 55 and 56: DRUM LIKE ME Tutorial >STEP-02 Ribb
Page 57 and 58: DRUM LIKE ME Tutorial Language >PYT
Page 59 and 60: MULTI BOOT ON A RASPBERRY PI 2 Tuto
Page 61 and 62: ADDITIVE SYNTHESIS Tutorial Languag
Page 63 and 64: YOUR QUESTIONS ANSWERED F.A.Q. FROM
Page 65: THE Official £12.99 200 pages of R
Page 69 and 70: UNDERSTAND OBJECT-ORIENTED PROGRAMM
Page 77 and 78: NEXTCLOUD BOX Review magpi.cc/2ivwj
Page 79 and 80: PAN-TILT HAT Review pimoroni.com £
Page 81 and 82: RASPIROBOT ROVER KIT Review magpi.c
Page 83 and 84: BOOKS Review RASPBERRY PI IOT IN C
Page 85 and 86: APL Community ROBOTS! ONE OF THE PR
Page 87 and 88: THIS MONTH IN PI Community CROWDFUN
Page 89 and 90: FEMI AND GRACE OWOLADE-COOMBES Comm
Page 91 and 92: EVENTS Community JAM HEAT MAP JAMS
Page 93 and 94: YOUR LETTERS Community FROM THE FOR
Page 96 and 97: Column THE FINAL WORD MATT RICHARDS
Page 99: Expand your Pi Stackable expansion
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