創建一類流

Question

我創建這是應該的DNA序列讀取類的打開文件：它包含一個如果流私有成員：

接口：

class Sequence_stream { 
    const char* FileName; 
    std::ifstream FileStream; 
    std::string FileFormat; 

public: 
    Sequence_stream(const char* Filename, std::string Format); 
    NucleotideSequence get(); 
}; 

實施：

Sequence_stream::Sequence_stream(const char* Filename, std::string Format) 
{ 
    FileName = Filename; 
    FileStream.open(FileName); 
    FileFormat = Format; 
    std::cout << "Filestream is open: " << FileStream.is_open() << std::endl; 
} 

NucleotideSequence Sequence_stream::get() 
{ 
    if (FileStream.is_open()) 
    { 
     char currentchar; 
     int basepos = 0; 
     std::string name; 
     std::vector<Nucleotide> sequence; 
     currentchar = FileStream.get(); 
     if (currentchar == '>' && false == FileStream.eof()) { // Check that the start of the first line is the fasta head character. 
      currentchar = FileStream.get(); // Proceed to get the full name of the sequence. Get characters until the newline character. 
      while(currentchar != '\n' && false == FileStream.eof()) 
      { 
       if (true == FileStream.eof()) { 
        std::cout << "The file ends before we have even finished reading in the name. Returning an empty NucleotideSequence" << std::endl; 
        return NucleotideSequence(); 
       } 
       name.append(1, currentchar); 
       currentchar = FileStream.get(); 
      } // done getting names, now let's get the sequence. 
      currentchar = FileStream.get(); 
      while(currentchar != '>' && false == FileStream.eof()) 
      { 
       if(currentchar != '\n'){ 
        basepos++; 
        sequence.push_back(Nucleotide(currentchar, basepos)); 
       } 
       currentchar = FileStream.get(); 
      } 
      if(currentchar == '>') 
      { 
       FileStream.unget(); 
      } 
      return NucleotideSequence(name, sequence); 
     } else { 
      std::cout << "The first line of the file was not a fasta format description line beginning with '>'. Are you sure the file is of FASTA format?" << std::endl; 
      return NucleotideSequence(); 
     } 

    } else { 
     std::cout << "The filestream is not open..." << std::endl; 
     return NucleotideSequence(); 
    } 
} 

但是如果我測試：

int main() 
{ 
    std::cout << "Let's try and read in a sequence!" << std::endl; 
    std::cout << "First we'll create a stream!" << std::endl; 
    Sequence_stream MyDNAStream("~/Dropbox/1_20dd5.fasta", "fasta"); 
    std::cout << "Done!" << std::endl; 
    std::cout << "Now let's try and get a sequence!" << endl; 
    NucleotideSequence firstsequence = MyDNAStream.get(); 
    return 0; 
} 

我看到，如果流不開放：

Let's try and read in a sequence! 
First we'll create a stream! 
Filestream is open: 0 
Done! 
The filestream is not open... 
logout 

[Process completed] 

雖然我還以爲構造函數打開，如果流。在創建對象幷包含開放流時，我需要做些什麼來糾正此問題？ （我知道我還沒有包含一個析構函數，它會在對象被破壞時關閉流）。

謝謝， 本。

Answer 1

您的示例顯示is_open返回false。我認爲你應該檢查你的構造函數，該文件確實是打開的，如果不是，則拋出。

在你的情況，我懷疑這是由於傳遞「〜/ Dropbox/1_20dd5.fasta」作爲輸入參數。你用完整的路徑名進行測試，沒有〜？我不知道處理實際路徑擴展的C++庫（如python的os.path）。