OC_UIAlertController基本使用

    UIAlertController * alertController = [UIAlertController alertControllerWithTitle:@"标题"
                                                                              message:@"message"
                                                                       preferredStyle:UIAlertControllerStyleAlert];
    
    [alertController addTextFieldWithConfigurationHandler:^(UITextField * _Nonnull textField) {
        
        textField.placeholder = @"userName";
        
    }];
    
    [alertController addTextFieldWithConfigurationHandler:^(UITextField * _Nonnull textField) {
        
        textField.placeholder = @"key";
        
    }];
    
    
    UIAlertAction * cancelAction = [UIAlertAction actionWithTitle:@"Cancel" style:UIAlertActionStyleCancel handler:^(UIAlertAction * _Nonnull action) {
        
    }];
    [alertController addAction:cancelAction];
    
    UIAlertAction * okAction = [UIAlertAction actionWithTitle:@"Default" style:UIAlertActionStyleDefault handler:^(UIAlertAction * _Nonnull action) {
        
    }];
    [alertController addAction:okAction];
    
    [self presentViewController:alertController animated:YES completion:nil];

UIAlertControllerStyleAlert

    UIAlertController * alertController = [UIAlertController alertControllerWithTitle:@"标题"
                                                                              message:@"message"
                                                                       preferredStyle:UIAlertControllerStyleActionSheet];
    
    UIAlertAction * cancelAction = [UIAlertAction actionWithTitle:@"Cancel" style:UIAlertActionStyleCancel handler:^(UIAlertAction * _Nonnull action) {
        
    }];
    [alertController addAction:cancelAction];
    
    UIAlertAction * okAction = [UIAlertAction actionWithTitle:@"Default" style:UIAlertActionStyleDefault handler:^(UIAlertAction * _Nonnull action) {
        
    }];
    [alertController addAction:okAction];
    
    UIAlertAction * DestructiveAction = [UIAlertAction actionWithTitle:@"Destructive" style:UIAlertActionStyleDestructive handler:^(UIAlertAction * _Nonnull action) {
        
    }];
    [alertController addAction:DestructiveAction];
    
    [self presentViewController:alertController animated:YES completion:nil];

UIAlertControllerStyleActionSheet