iphone - AFNetworking SPARQL查询失败，URL错误

Question

我有以下使用AFNetworking来获取山脉列表的iOS代码。我在故障块中收到“错误的URL”错误。

 - (void) loadMountains
{
    NSString * loadMountainQueries = @"select * where { ?Mountain a dbpedia-owl:Mountain; dbpedia-owl:abstract ?abstract. FILTER(langMatches(lang(?abstract),"EN")) } ";        
    NSString * urlString = [NSString stringWithFormat:@"http://dbpedia.org/sparql/?query=%@",loadMountainQueries];

    NSLog(@"%@", urlString);

    NSURL *url = [NSURL URLWithString:urlString];
    NSURLRequest *request = [NSURLRequest requestWithURL:url];    

    AFHTTPRequestOperation *operation = [[AFHTTPRequestOperation alloc] initWithRequest:request];

    [AFHTTPRequestOperation addAcceptableContentTypes:
     [NSSet setWithObjects:@"application/json", @"sparql-results+json", @"text/json", @"text/html", @"text/xml", nil]];

    [operation setCompletionBlockWithSuccess:^(AFHTTPRequestOperation *operation, id responseObject)
    {
        NSLog(@"Response %@", [operation responseString]);
    }
    failure:^(AFHTTPRequestOperation *operation, NSError *error)
    {
        NSLog(@"Response %@", [operation responseString]);
        NSLog(@"Error: %@", error);
    }];

    [operation start];
}

我假设AFHTTPRequestOperation自动对URL进行编码，但是可以肯定的是-当我使用编码URL时，它会给出相同的响应“Bad URL”。在Safari中工作的同一查询在 objective-c 中无法工作。

我究竟做错了什么？

Answer 1

首先，第一行出现语法错误:

NSString * loadMountainQueries = @"select * where { ?Mountain a dbpedia-owl:Mountain; dbpedia-owl:abstract ?abstract. FILTER(langMatches(lang(?abstract),"EN")) } ";
---------------------------------------------------------------------------------------------------------------------------------------------------------^

您应该使用反斜杠转义引号:

... ang(?abstract),\"EN\")) } ";

现在的答案是:在将loadMountainQueries附加到主URL字符串之前，您必须％编码:

NSString *loadMountainQueries = @"select * where { ?Mountain a dbpedia-owl:Mountain; dbpedia-owl:abstract ?abstract. FILTER(langMatches(lang(?abstract),\"EN\")) } ";
NSString *encodedLoadMountainQueries = [loadMountainQueries stringByAddingPercentEscapesUsingEncoding:NSUTF8StringEncoding];
NSString *urlString = [NSString stringWithFormat:@"http://dbpedia.org/sparql/?query=%@",encodedLoadMountainQueries];

该网址在Safari中有效，因为它会自动对您的网址进行百分比编码。