Download
naming n.
Skip this Video
Loading SlideShow in 5 Seconds..
Naming PowerPoint Presentation

Naming

135 Views Download Presentation
Download Presentation

Naming

- - - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

  1. Naming

  2. General • Highly important • Understandability without delving into details • Classes – Nouns • File • Account • SymbolTable • Methods – Verbs • open() • withdraw() • lookup()

  3. General (Cont.) • Popularity • Scope • Rule of thumb: No good name -> Redesign the class • Avoid hiding of fields with variables • A good metaphor may help: Figure, Page

  4. Types • Nouns: Figure, Account • Sometimes –er suffix: Formatter, Loader • Popularity => Simple name • Frequent usage: typing a variable • Frequent usage: superclass • Communicate similarities & differences • Add a prefix to the superclassclass TextFormatter extends Formatter { ... } • Avoid “Object” in class names • Single form for enum typesenum Pet { CAT, DOG }

  5. Interfaces vs .Classes • Interfaces will usually be a popular typeclass ColoredFigure implements Figure { ... } • -able is a common suffix for interfaces • Denotes a mixin-like protocol unit • If both interface & concrete class are popular abstract class AbstractFigure implements IFigure { ... } • class Figureextends AbstractFigure { ... }

  6. Common Naming Schemes

  7. Methods • Verbs: paint(), remove() • boolean setters/getters • isVisible() • setVisible(boolean) • show(), hide() // More explicit • Getters • getX() • x() • Setters • setX(int) • x(int)

  8. Variables • result • results • count, n • curr, each • i, j • arg • List<Message> messages • Map<String,String> addressFromName • that • lhs, rhs • iconA, iconB • Event event; Painter painter; • Event e; Painter p; • isEmpty; // Better than: if(!notEmpty) ...

  9. <hungarian.notation>

  10. Hungarian Notation is Bad • Prefix specifies the type/stroage of the variable • C • ulDistance = Unsigned Long • bEnabled = Boolean • paulData = Pointer to Array of Unsigned Long • szName = Zero terminated String • Java • pX = Parameter • fY = Field (sometimes “m” for Member) • sfZ = Static Field • Considered outdated (or even evil) • Overly verbose • Obviated by: smart IDEs, short methods/classes

  11. Hungarian Notation is Great • Prefix specifies “pseudo subtype” • Pseudo subtypes examples: • Integers: Row vs. Column • Integers: Dollars vs. Cents • Strings: text vs. HTML

  12. Is Address HTML-ed? • String str = person.getDetails(“address”);...String adr = str;...record.setField(“location", adr); • ...String address = record.getField(“location"); • ...out.println(“Send to: <i>” + address + “</i>”); • // Did we remember to call htmlEncode() ??

  13. Hungarian Notation to the Rescue • Let’s apply the following convention: • Strings coming from the user are considered text • Must be stored in variables prefixed with “t” • The same goes for database columns • htmlEncode() translates a “t” prefix to “h” • Strings returned from htmlEncode() are considered HTML • Must be stored in a variable prefixed with “h” • Assignments allowed only if prefixes match

  14. Is tAddress HTML-ed? • String tStr = person.getDetails(“address”);...String tAdr = tStr;...record.setField(“tLocation", tAdr);...String tAddress = record.getField(“tLocation");...out.println(“Send to: <i>” + tAddress + “</i>”); • // Clearly, tAddress was not htmlEnocde-d

  15. Rename: tAddress => hAddress • String tStr = getOrderDetails(“address”);...String tAdr = tStr;...record.setField(“tLocation", tAdr);...String hAddress = record.getField(“tLocation"); // violation of our convention !! • ...out.println(“Send to: <i>” + hAddress + “</i>”);

  16. Correct Code – All Prefixes Match • String tStr = getOrderDetails(“address”);...String tAdr = tStr;...record.setField(“tLocation", tAdr);...String hAddress = htmlEncode(record.getField(“tLocation"));...out.println(“Send to: <i>” + hAddress + “</i>”);

  17. </hungarian.notation>

  18. </naming>

  19. Eyetracking

  20. Benefits of Narrow Code • We don’t read stuff on the right-hand side • Stacktrace • Debugability of if statements • Debugability of return values • Explaining variables • => Prefer tall, narrow code • Over short, wide

  21. Fix it in the language • “For example, I want the next C grammar to define that a space comes between any keyword and an opening parenthesis. "if (foo)" would be legal, but "if(foo)" would not. Not a warning, not optionally checked, but actually forbidden by the language parser. Flat out illegal. Can't compile. • ... • There is not now, nor will there ever be, a programming style whose benefit is significantly greater than any of the common styles. Get real. Discovering a style that improves your productivity by more than a few percent over the common styles is about as likely as discovering a new position for sex.” • Ken Arnold, “Style is Substance” • www.artima.com