Objective-C Fundamentals

Creating NSError objects
207
chapters to follow along, by all means do so. Creating a new View-based application
in Xcode should get you on the right track. Otherwise you can always examine the
RentalManagerAPI project in the downloadable source code for this chapter.
Take a look at the code in the following listing.
Listing 10.3
RentalManagerAPI.h
#import
extern NSString * const RMAMissingValuesKey;
extern NSString * const RMAAccountExpirationDateKey;
extern NSString * const RMAErrorDomain;
enum {
RMAValidationError = 1,
RMAAccountExpiredError = 2,
RMAWrongCredentialsError = 3
};
@interface RentalManagerAPI : NSObject {
Required value missing
Account expired
Wrong user/password
}
+ (BOOL)publishAd:(NSDictionary *)anAd
error:(NSError **)anError;
@end
The next listing contains the rest of the code.
Listing 10.4
RentalManagerAPI.m
#import "RentalManagerAPI.h"
Define custom
NSString * const RMAErrorDomain =
error domain
@"com.my-awesome-rental-manager.API";
NSString * const RMAMissingValuesKey = @"RMAMissingValuesKey";
NSString * const RMAAccountExpirationDateKey =
@"RMAAccountExpirationDateKey";
@implementation RentalManagerAPI
+ (BOOL)publishAd:(NSDictionary *)anAd error:(NSError **)anError {
if (anAd == nil) {
@throw [NSException exceptionWithName:@"RMABadAPICall"
}
reason:@"anAd dictionary is nil"
userInfo:nil];
NSMutableArray *missingValues = [NSMutableArray array];
for (NSString *key in [@"name price city"
componentsSeparatedByString:@" "]) {
if ([[anAd objectForKey:key] length] == 0) {
[missingValues addObject:key];
}
Check values
}
missing, if any
if ([missingValues count] > 0) {
If no ad object,
throw an exception