问将位置存储为字符串，从字符串中返回位置以在地图上显示。iOS

EN

@interface CLLocationToStringTransformer : NSValueTransformer 
@end

@implementation CLLocationToStringTransformer

+ (BOOL) allowsReverseTransformation 
{ return YES; }

+ (Class) transformedValueClass
{ return [NSString class]; }

- (id) transformedValue: (id) value 
{ CLLocation *location = (CLLocation *) value;
  return [NSString stringWithFormat: "%@ %@",
                   theLocation.coordinate.latitude,
                   theLocation.coordinate.longitude]; } 

- (id)reverseTransformedValue:(id)value 
{ NSString *string = (NSString *) value;
  NSArray  *parts  = [string componentsSeparatedByString: @" "];
  return [[CLLocation alloc] initWithLatitude: [parts[0] doubleValue]
                                    longitude: [parts[1] doubleValue]]; }
@end