Programming In Scala: Chapter#6,7 notes

Ch6-
Fuctional objects = immutable objects, this chapter basically shows you how to write class for immutable Rational object. Many key concepts of writing classes in scala are covered.

In scala class, Two kind of constructors, primary and auxiliary. Its mandatory that an auxiliary constructor invokes anothe constructor.
Only primary constructor can invoke the constructor of superclass.

In scala class, Getters and setters are "generated" only for the field variables(unless they are declared private)

override keyword needs to be explicitly used when overriding a method of the superclass.

Though scala compiler allows you to use '$' in identifier name, but it *MUST NOT* be used as its reserved for identifiers generated by scala compiler and there may be clashes.

Conventionally, identifiers for constants in java are like X_OFFSET, but in scall its recommended to use only first letter capital for constants and same identifier in scala should be XOffset.

A literal identifier trick can be used if you want to use a reserved word as identifier. A literal identifier is an identifier enclosed in back quotes.

Method overloading is supported that is same method name can be used for two different methods as long as there is some difference in method signature.

There is an implicit conversion trick that allows you to convert any type into any other type. Its very powerful but highly recommended not to be used and hence I'm not even mentioning here how its done :)

Ch7-
if, while, do-while, for, try, match - all return some value

Scala assignment always returns the unit value, ().

It recommends to use recursion rather than while loops to achieve the same effect.

for loop is swiss army knife in scala(seems inspired from loop macro in lisp), it can be used to do many different iteration tasks. Please see section 7.3 for its usage.


Scala's exceptions behave like same in java, thrown using throw keyword.Catching exception syntax is different a little bit and seems to less the code needed in handling multiple exceptions.

If a method throws an exception, its not mandatory for it to declare it using the throws as in java.

finally keyword is also available whose behavior is exactly as that in java.

"Match" is "switch" of java. However switch allows only matching of integers and enums whereas "Match" lets you select using arbitrary patterns.