Qt Creator IDE doesn't suggest the methods

[expert_vision]

I'm a total newbie to OOP but I know this, whenever I type "." next to an object, IDE nicely shows me all of it's methods and functions. But not in this case:

void Widget::on_Start_clicked()
{
    ...
    QTextStream stream(&file);
    QString content = stream.readAll();
    QStringList lines = content.split("\\n");
    lines.at(0).

void Widget::on_Start_clicked()
{
    ...
    QTextStream stream(&file);
    QString content = stream.readAll();
    QStringList lines = content.split("\\n");
    lines.at(0).

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but if I do this:

void Widget::on_Start_clicked()
{
    ...
    QTextStream stream(&file);
    QString content = stream.readAll();
    QStringList lines = content.split("\\n");
    QString line = lines.at(0);
    line.

void Widget::on_Start_clicked()
{
    ...
    QTextStream stream(&file);
    QString content = stream.readAll();
    QStringList lines = content.split("\\n");
    QString line = lines.at(0);
    line.

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it works.

So .. what's going on?