sensorario sensorario - 17 days ago 5
Objective-C Question

"for x in" syntax with NSArray

I've this kind of instruction:

[self someMethod:CGPointMake(50, 50)];
[self someMethod:CGPointMake(270, 50)];
[self someMethod:CGPointMake(50, 360)];
[self someMethod:CGPointMake(270, 360)];
...


I want to refactor code using NSArray like this:

NSArray items = [NSArray initWithObjects:
CGPointMake(50, 50),
CGPointMake(270, 50),
CGPointMake(50, 360),
CGPointMake(270, 360),
...
nil];


I dont know right syntax, can someone help me? I'd tried with this, but XCode tells me "Selector element type CGPoint is not a valid object":

CGPoint point = [CGPoint alloc];

for (point in items) {
[self someMethod:point];
}

Answer

for-in loops are an Objective-C concept for iterating over collection classes (that conform to NSEnumeration). If you would like to iterate over C-structs (like CGPoints), use a standard for-loop with a C-array, or wrap the CGPoints in NSValues.

Here's what your refactoring would look like in modern Objective-C syntax:

NSArray *items = @[
                  [NSValue valueWithPoint:CGPointMake(50, 50)], //wrap the points in an
                  [NSValue valueWithPoint:CGPointMake(270, 50)], //NSValue so they become
                  [NSValue valueWithPoint:CGPointMake(50, 360)], //first class citizens
                  [NSValue valueWithPoint:CGPointMake(270, 360)],//(Y no boxing?*)
                 ]; //End of collection literal
for (NSValue *value in items) { //iterate through the NSValues with our points
    [self someMethod:[value pointValue]]; //'un-wrap' the points by calling -pointValue
}

*My personal struct boxing macro:

#define STRUCT_BOX(x) [NSValue valueWithBytes:&x objCType:@encode(typeof(x))];