03-control-flow-and-error-handling.md

Control Flow & Error Handling

Conditional Statements.

A conditional statement is a set of commands that executes if a specified condition is true.

If...else (kama...sivyo) statement

Use the kama statement to execute a statement if a logical condition is true. Use the optional sivyo clause to execute a statement if the condition is false.

A kama statement looks like this:

kama (condition) {
  statement_1
} sivyo {
  statement_2
}

Here, the condition can be any expression that evaluates to kweli or uwongo.

You can also compound the statements using au to have multiple conditions tested in sequence, as follows:

kama (condition_1) {
  statement_1
} au (condition_2) {
  statement_2
} au (condition_n) {
  statement_n
} sivyo {
  statement_last
}

Exception handling statements

You can handle runtime exceptions using the jaribu...iwapo statements

jaribu...iwapo statement

You can throw exceptions using the tupa statement and handle them using the jaribu...iwapo statements

tupa statement

Use the tupa statement to throw an exception. A tupa statement specifies the value to be thrown:

tupa expression

The jaribu...iwapo statement marks a block of statements to try, and specifies one or more responses should an exception be thrown. If an exception is thrown, the jaribu...iwapo statement catches it.

The following example uses a jaribu...iwapo statement. The example calls a function that divides two numbers. If the value for y is 0, an exception is thrown since division by 0 is invalid, and the statements in the iwapo block set the jibu variable to 0.

shughuli gawa(x, y) {
  rudisha x / y
}

jaribu { // statements to try
  jibu = gawa(12, 0) // function could throw exception
} iwapo (shida) {
  jibu = 0
  andika(shida)
}

The iwapo block

You can use a iwapo block to handle all exceptions that may be generated in the jaribu block.

iwapo (shida) {
  statements
}

The iwapo block specifies an identifier (shida in the preceding syntax) that holds the value/message of the exception. You can use this identifier to get information aobut the exception that was thrown.

jaribu {
  tupa 'My exception (shida yangu)' // generates an exception
} iwapo (shida) {
  // statement to handle any exceptions
  andika(shida) // log exception to console
}

The mwishowe block

The mwishowe block contains statements to be executed after the try and catch blocks execute. Additionally, the mwishowe block executes before the code that follows the jaribu...iwapo...mwishowe statement.

funguaFaili()

jaribu {
  andikaFaili(data) // this may throw an error
} iwapo (shida) {
  chunguzaShida(shida) // if an error occurred, handle it
} mwishowe {
  fungaFaili() // always close the resource
}