如何將NSString轉成NSNumber

//新增一個numberFormatter

NSNumberFormatter *numberFormatter = [[NSNumberFormatter alloc] init];

//將style設定為NSNumberFormatterDecimalStyle

numberFormatter.numberStyle = NSNumberFormatterDecimalStyle;

//NSString轉成NSNumber

NSNumber *piNumber = [numberFormatter numberFromString:@"3.141592654"];

Note.若數字格式不正確，則piNumber會被指定為nil。