ios - 不兼容的 block 指针类型 - Objective-c

Question

我想在主线程中使用 return 语句调用以下代码，但出现以下错误。

Incompatible block pointer types passing 'NSString *(^)(void)' to parameter of type 'dispatch_block_t _Nonnull' (aka 'void (^)(void)')

以下是我的代码。

NSString *hash = [AGMobileService accessTokenHashForDate:date withParameters:[NSArray new]];


+ (NSString *)accessTokenHashForDate:(NSDate *)date withParameters:(NSArray *)params{

    dispatch_async(dispatch_get_main_queue(), ^{
      NSString *accessToken = ((AppDelegate *)[[UIApplication sharedApplication] delegate]).loginProfile.accessToken;

      NSString *paramsStr = [params componentsJoinedByString:@""];
      NSString *hashStr = [NSString stringWithFormat:@"%@%@%@%@", [CommonUtil IMEI], [date agileHashFormattedString], (!paramsStr) ? @"" : paramsStr, accessToken];
      return [AGMobileService computeHash:hashStr usingHash:HASH_SALT];
    });
}

+ (NSString *)computeHash:(NSString *)text usingHash:(NSString*)hashSalt {

    NSString *textToEncode = [NSString stringWithFormat:@"%@%@", hashSalt, text];
    NSData *data = [textToEncode dataUsingEncoding:NSUTF8StringEncoding];
    unsigned char hash[CC_SHA256_DIGEST_LENGTH];
    if ( CC_SHA256([data bytes], (int) [data length], hash) ) {
        NSData *sha256 = [NSData dataWithBytes:hash length:CC_SHA256_DIGEST_LENGTH];
        return [sha256 base64EncodedString];
    }
    return nil;
}

Answer 1

我也遇到过这样的事情，只是把dispatch block 中的返回码去掉了，但是不知道原因，所以我也想知道原因。