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

Question

I have downloaded sample code for SQLite learning. I'm using Xcode 6.1.1 and iPhone 6 plus simulator. After running app on simulator I'm getting DB Error : unknown error from query execution. Below is part of code where I'm getting warning as Comparison of constant 101 with expression of type 'BOOL' (aka 'bool') is always false.

// 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));
  }

What might be fix for this?

Answer 1

Checking condition for compiledStatement directly solved the problem :

// 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

Try changing Your code

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

That's beacause TRUE is probaly 1 or -1, but never 101 (SQLITE_DONE = 101). Boolean values are true and false but never SQLITE_DONE .

You could write something like

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

But if don't need this result later, there is no point in defining this variable at all

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

Answer 4

I know it's late,but it can help someone in future .

// 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));
                }