SQLite iOS警告：常量101与BOOL类型表达式的比较始终为false

Question

我已经下载了SQLite学习的示例代码。我正在使用Xcode 6.1.1和iPhone 6 plus模拟器。在模拟器上运行应用程序后，我从查询执行中获取DB Error : unknown error。以下是我收到Comparison of constant 101 with expression of type 'BOOL' (aka 'bool') is always false.

警告的代码的一部分

// Execute the query.
BOOL executeQueryResults = sqlite3_step(compiledStatement);
 if (executeQueryResults == SQLITE_DONE) {
     // Keep the affected rows.
      self.affectedRows = sqlite3_changes(sqlite3Database);

       // Keep the last inserted row ID.
       self.lastInsertedRowID = sqlite3_last_insert_rowid(sqlite3Database);
  }
  else {
      // If could not execute the query show the error message on the debugger.
       NSLog(@"DB Error: %s", sqlite3_errmsg(sqlite3Database));
  }

可能有什么办法解决这个问题？

Answer 1

检查 compiledStatement 的条件直接解决了问题：

// Execute the query.
// BOOL executeQueryResults = sqlite3_step(compiledStatement);
// if (executeQueryResults == SQLITE_DONE) {

 if (sqlite3_step(compiledStatement)) {
     // Keep the affected rows.
      self.affectedRows = sqlite3_changes(sqlite3Database);

      // Keep the last inserted row ID.
       self.lastInsertedRowID = sqlite3_last_insert_rowid(sqlite3Database);
 }
 else {
     // If could not execute the query show the error message on the debugger.
       NSLog(@"DB Error: %s", sqlite3_errmsg(sqlite3Database));
 }

Answer 2

尝试更改您的代码

if (sqlite3_step(compiledStatement) == SQLITE_DONE) {
     // Keep the affected rows.
      self.affectedRows = sqlite3_changes(sqlite3Database);

       // Keep the last inserted row ID.
       self.lastInsertedRowID = sqlite3_last_insert_rowid(sqlite3Database);
  }
  else {
      // If could not execute the query show the error message on the debugger.
       NSLog(@"DB Error: %s", sqlite3_errmsg(sqlite3Database));
  }

Answer 3

因为TRUE可能是1或-1，但从不101（SQLITE_DONE = 101）。布尔值为true和false，但绝不是SQLITE_DONE。

你可以写点像

bool done = sqlite3_step(compiledStatement) == SQLITE_DONE;
if (done) {
    ...
}

但是如果以后不需要这个结果，那么在所有

中定义这个变量是没有意义的

if (sqlite3_step(compiledStatement) == SQLITE_DONE) {
    ...
}

Answer 4

我知道现在已经很晚了，但将来可以帮助别人。

// This is the case of an executable query (insert, update, ...).

                // Execute the query.
                BOOL executeQueryResults = sqlite3_step(compiledStatement);
                if (executeQueryResults) {
                    // Keep the affected rows.
                    self.affectedRows = sqlite3_changes(sqlite3Database);
                    NSLog(@"affected row = %d",self.affectedRows);

                    // Keep the last inserted row ID.
                    self.lastInsertedRowID = sqlite3_last_insert_rowid(sqlite3Database);
                    NSLog(@"last iserted row = %lld",self.lastInsertedRowID);
                }
                else {
                    // If could not execute the query show the error message on the debugger.
                    NSLog(@"DB Error: %s", sqlite3_errmsg(sqlite3Database));
                }