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我创建了一个字符串,我已经用__block标识符作为前缀,这样我就可以在我的块之外访问该变量。然而,一旦我尝试运行应用程序中的变量返回“零”:块运行后__block变量返回nil
-(void)downloadParcelData {
__block NSString *test;
MKMapRect mRect = self.mapView.visibleMapRect;
NSArray *array = [NSArray array];
array = [self getBoundingBox:mRect];
NSString *polygonString = [self convertCoordinates:array];
AFHTTPSessionManager *manager = [AFHTTPSessionManager manager];
manager.responseSerializer.acceptableContentTypes = nil;
NSDictionary *parameters = @{@"client" : @"xxxxxxxxxx",
@"spatial_intersect" : [NSString stringWithFormat:@"POLYGON((%@))", [polygonString stringByAddingPercentEncodingWithAllowedCharacters:[NSCharacterSet URLHostAllowedCharacterSet]]]};
[manager GET:@"someURL" parameters:parameters progress:nil success:^(NSURLSessionTask *task, id responseObject) {
NSLog(@"JSON: %@", responseObject);
test = responseObject[@"txn_id"];
} failure:^(NSURLSessionTask *operation, NSError *error) {
NSLog(@"Error: %@", error);
}];
[self fetchParcelData:test];
}
为什么这可能发生的任何想法?提前致谢。