Learning the iOS 4 SDK for JavaScript Programmers

Program Flow Constructions

When it comes to program flow controls, your JavaScript experience gets you almost all of the way there. The following C/Objective-C prototypes should all look familiar to you (showing the multiple-line statement version with curly braces and optional items in brackets):

if (conditionExpression) {
    statementsIfTrue
}

if (conditionExpression) {
    statementsIfTrue
} else {
    statementsIfFalse
}

result = (conditionExpression) ? expression1 : expression2;

while (conditionExpression) {
    statementsIfTrue
}

do {
    statements
} while (conditionExpression)

for (initializationExpression; conditionExpression; updateExpression) {
    statements
}

switch (expression) {
    case labelN:
        statements
        [break;]
    ...
    [default:
        statements]
}

Because the comparison operators you use in C/Objective-C are the same ones you know from JavaScript, you already know what to do with all of the conditionExpression placeholders. The only construction you need to watch carefully is the for repeat loop. Be sure that the counter variable you initialize in the initializationExpression has a data type associated with it. You can specify the data type in a separate statement above the for loop or in the expression itself:

int i;
for (i = 0; i < maxValue; i++) {...}

for (int j = 0; j < maxValue; j++) {...}

Bear in mind the discussion earlier in this chapter about scope with regard to the loop counting variable. If you need the variable value after the loop completes, be sure to declare the variable before the loop. ...