Warning: Implicit conversion loses Integer precision in xcode 6

Question

I know it could be a duplicate, but i got about 30 Implicit conversion loses Integer precision warnings in my ios project after updating xcode to version 6.

First Example:

NSArray * stations = [self stationsJSON][KEY_ITEM_LIST];

int newSize = (stations.count + 1); // Implicit conversion loses Integer precision: 'unsigned long' to 'int'

Second Example:

- (UITableViewCell *)tableView:(UITableView *)tableView cellForRowAtIndexPath:(NSIndexPath *)indexPath {
    ...
    int index = indexPath.row / 2; // Implicit conversion loses Integer precision: 'long' to 'int'
    ...
}

I know what the warning means. Using NSInteger can help to avoid this warning.

I don't understand, why there was no warnings in xcode 5? And why there is no warning after i change the line

int index = indexPath.row / 2;

to

int index = indexPath.row / 2i;

Answer 1

NSArray count is NSUInteger.

NSIndexPath row is NSInteger.

On 64-bit systems, NSUInteger and NSInteger are 64-bits but int is 32-bit. So the value won't fit which results in the warning.

It's best to avoid int in iOS. Instead, use the same type as the values you are dealing with.

NSInteger index = indexPath.row / 2;

You probably see these in Xcode 6 due to the default warnings. You can easily see these in Xcode 5 with the right warning settings and building for 64-bit.

Answer 2

You can update project settings, to remove all

Implicit conversion loses integer precision warnings, by setting

Implicit Conversion to 32 Bit Type to No

in project's build settings.

Answer 3

I was always annoyed by these warnings, so I came up with simple solution to avoid it:

@interface NSIndexPath(UnsignedIndex)

@property (nonatomic, readonly) NSUInteger sectionIndex;
@property (nonatomic, readonly) NSUInteger rowIndex;

@end

@implementation NSIndexPath(UnsignedIndex)

- (NSUInteger)sectionIndex {

    return (NSUInteger)self.section;
}

- (NSUInteger)rowIndex {

    return (NSUInteger)self.row;
}

@end

Simply use rowIndex and sectionIndex properties from this category instead of NSIndexPath's row and section properties.