use Underline in wild card charecter of Like query gives wrong result

●Question

Why the SQL execution always return the wrong result when i use 'underline' ?

select  * 

from  user

where  userid like 'Karen_Chang%'  

●Solution

Use brackets! []

select  * 

from  user

where  userid like 'Karen[_]Chang%'

break label usage in Objective-C and Java

if you have nested for loop or the for loop need to be break in special condition
use 'break label' can satisfy your demand

●Java
myForLoop: {
    for (; ; ;) {
if(someCondition == True)
            break myForLoop;
    }
}

●Objective-C
for (;;)
{
    for (;;)
    {
        break; /* breaks inner loop */
    }
    for (;;)
    {
        goto myForLoop; /* breaks outer loop */
    }
}
myForLoop:;

Swipe to delete UITableViewCell

●iOS (2.0 and later)

- (BOOL)tableView:(UITableView *)tableView canEditRowAtIndexPath:(NSIndexPath *)indexPath {

    return YES;

}

- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath {

    if (editingStyle == UITableViewCellEditingStyleDelete) {

        [self.myData removeObjectAtIndex:indexPath.row];

        [tableView reloadData];

    }

}

●iOS (8.0 and later)

- (BOOL)tableView:(UITableView *)tableView canEditRowAtIndexPath:(NSIndexPath *)indexPath {

    return YES;

}

- (NSArray *)tableView:(UITableView *)tableView editActionsForRowAtIndexPath:(NSIndexPath *)indexPath {

    UITableViewRowAction *deleteAction = [UITableViewRowAction rowActionWithStyle:UITableViewRowActionStyleDestructive title:@"delete" handler:^(UITableViewRowAction *action, NSIndexPath *indexPath) {

        [self.myData removeObjectAtIndex:indexPath.row];

        [tableView reloadData];

    deleteAction.backgroundColor = [UIColor redColor];

    return @[deleteAction];

}

But swipe to delete doesn't work at iOS8 
It's Apple's Bug!!!

How to solve?
add the old method 'commitEditingStyle' as below

- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath {

}

Although the Objective-C has the description about the commitEditingStyle as following, iOS 8 is still not working without this method T__T

// After a row has the minus or plus button invoked (based on the UITableViewCellEditingStyle for the cell), the dataSource must commit the change

// Not called for edit actions using UITableViewRowAction - the action's handler will be invoked instead

- (void)tableView:(UITableView *)tableView commitEditingStyle:(UITableViewCellEditingStyle)editingStyle forRowAtIndexPath:(NSIndexPath *)indexPath;

[Reprinted]How to show UIDatePicker in UITableViewCell

針對DatePicker已有很多第三方元件，都很棒但不符合目前專案的需求，最終還是使用原生的UIDatePicker打造iPhone行事曆的效果

作法不難，只轉載一些很不賴的參考資訊

iOS Show UIPickerView between UITableViewCells

make uipickerview appear between cells when touched cell

iOS 7 in-line UIDatePicker – Part 1

ToolBar done button action does not work on UIDatePicker

How to show uidatepicker from uitableviewcell

如果要直接用第三方元件，有這些

RMDateSelectionViewController

AIDatePickerController

How to use NSDefault

Primitive Object
// Get
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
NSString* userId = [defaults objectForKey:@"UserId"];
[defaults synchronize];

// Set
NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];
[defaults setObject:userId forKey:@"UserId"];
[defaults synchronize];

// Clear

NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];

[defaults removeObjectForKey:@"UserId"];

[defaults synchronize];

Custom Object

// Get

NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];

NSData *formData = [defaults objectForKey:@"CustomObject"];

MyCustomData *data=[NSKeyedUnarchiver unarchiveObjectWithData:data];

[defaults synchronize];

// Set

NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];

NSData *data = [NSKeyedArchiver archivedDataWithRootObject:myCustomObject];

[defaults setObject:data forKey:@"CustomObject"];

[defaults synchronize];

// Clear

NSUserDefaults *defaults = [NSUserDefaults standardUserDefaults];

[defaults removeObjectForKey:@"CustomObject"];

[defaults synchronize];