ios5 - 等待 CLGeocoder 完成并发枚举

Question

我在类方法中有以下代码

NSDictionary *shopAddresses = [[NSDictionary alloc] initWithContentsOfFile:fileName];
NSMutableArray *shopLocations = [NSMutableArray arrayWithCapacity:shopAddresses.count];

[shopAddresses enumerateKeysAndObjectsWithOptions:NSEnumerationConcurrent usingBlock:^(id key, ShopLocation *shopLocation, BOOL *stop) {
    CLGeocoder *geocoder = [[CLGeocoder alloc] init];
    [geocoder geocodeAddressString:shopLocation.address completionHandler:^(NSArray *placemarks, NSError *error) {
        if (error) {
            NSLog(@"Geocode failed with error: %@", error);
        }
        else {
            shopLocation.placemark = [placemarks objectAtIndex:0];
        }
        [shopLocations addObject:shopLocation];
    }];
}

执行此代码后，我想返回 shopLocations 数组作为该方法的结果。但是，如果我不希望数组为空，我需要以某种方式等到所有地理编码器搜索完成。

我怎样才能做到这一点？

我尝试了不同的 GCD 方法，但到目前为止还没有成功。

Answer 1

这可以由dispatch_group_...函数处理：

…
dispatch_group_t group = dispatch_group_create();

[shopAddresses enumerateObjectsUsingBlock:^(id key, NSUInteger idx, BOOL *stop) {

    dispatch_group_enter(group);

    CLGeocoder *geocoder = [[CLGeocoder alloc] init];
    [geocoder geocodeAddressString:shopLocation.address completionHandler:^(NSArray *placemarks, NSError *error) {
        if (error) {
            NSLog(@"Geocode failed with error: %@", error);
        }
        else {
            shopLocation.placemark = [placemarks objectAtIndex:0];
        }
        [shopLocations addObject:shopLocation];

        dispatch_group_leave(group);
    }];
}];

while (dispatch_group_wait(group, DISPATCH_TIME_NOW)) {
    [[NSRunLoop currentRunLoop] runMode:NSDefaultRunLoopMode
                             beforeDate:[NSDate dateWithTimeIntervalSinceNow:1.f]];
}
dispatch_release(group);

…

我正在使用这些块来积累一些网络请求。

我希望这会有所帮助。