How to break block loop in Objective - C? - objective-c

Question

I have these declarations in header file:
Note: I won't explain the whole code, I think it is easy to understand
typedef void (^loopCell)(id cell);
-(id)allCells:(loopCell)cell;
And allCells function implementation:
-(id)allCells:(loopCell)cell
{
for (AAFormSection *section in listSections)
{
for (id _cell in section.fields) {
cell(_cell);
}
}
return nil;
}
The usage of allCells function:
-(void)setFieldValue:(NSString *)value withID:(int)rowID
{
[self allCells:^(id cell) {
if([cell isKindOfClass:[AAFormField class]]) {
AAFormField *_cell = (AAFormField *)cell;
if(_cell.rowID == rowID) {
_cell.value = value;
//return; Here I want to terminate loop
}
}
}];
}
My problem is, I can't terminate allCells loop in the middle (actually when I found object I need in the loop, I don't want iterate through other objects)
How can I stop allCells loop in the middle?

Answer 1

Look at the docs for NSArray enumerateObjectsUsingBlock:. They setup the block signature to take a BOOL pointer. Set the stop BOOL to YES to cause the iteration to stop.
typedef void (^loopCell)(id cell, BOOL *stop);
-(id)allCells:(loopCell)cell {
BOOL stop = NO;
for (AAFormSection *section in listSections) {
for (id _cell in section.fields) {
cell(_cell, &stop);
if (stop) {
break;
}
}
if (stop) {
break;
}
}
return nil;
}
-(void)setFieldValue:(NSString *)value withID:(int)rowID {
[self allCells:^(id cell, BOOL *stop) {
if([cell isKindOfClass:[AAFormField class]]) {
AAFormField *_cell = (AAFormField *)cell;
if(_cell.rowID == rowID) {
_cell.value = value;
if (stop) {
*stop = YES;
}
}
}
}];
}

Answer 2

You can't break from setFieldValue, but you can from allCells.
It's up to the method you're using that calls the block — allCells in this case — to provide a mechanism for stopping the loop. Usually, it's a parameter to the block.
If allCells is yours and you don't mind modifying it, you modify the block signature to take a pointer to a BOOL, initialized to YES, and check if the block modified it to NO.
(Note: You can break from a for in loop.)