Ios – How to add separators between UITableView sections

cocoa-touchiosswiftuikituitableview

I'm implementing a tableview, which has 3 sections(section count remain static) and each section contain several rows.

Behaviour 1: Add section header to only the third section.

How did I achieve:

func tableView(_ tableView: UITableView, viewForHeaderInSection section: Int) -> UIView? {
    if section == 2 {
       //create and return header view
    }
    return UIView(frame: CGRect(x: 0, y:0, width: tableView.width, height: UIScreen.main.scale))
}

Behaviour 2: TableViewCells shouldn't have separator. But, Sections should be separated with a thin line. (similar to tableviewcell separator)

What did I try:

Add a one pixel height, tableView width UIView, with all required properties set(color, etc) and add it as a sub-view to the section header view's
Add drop shadow with CGPoint(0,1) to the section header views

None of them worked out.

How did I achieve this:

Find last cell in every section,
Create an UIView with 1px height, tableView's width and add it as a subview to the last cell

Though this seem to work. I feel, there must be a better way of doing this, rather than adding line to bottom of every section's last tableView cell. Does anyone know a better way of implementing such behaviour?

Best Answer

Set the Style of the Table View to Grouped:

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All you have to do is set the selection style on the UITableViewCell instance using either:

Objective-C:

cell.selectionStyle = UITableViewCellSelectionStyleNone;

[cell setSelectionStyle:UITableViewCellSelectionStyleNone];

Swift 2:

cell.selectionStyle = UITableViewCellSelectionStyle.None

Swift 3 and 4.x:

cell.selectionStyle = .none

Further, make sure you either don't implement -tableView:didSelectRowAtIndexPath: in your table view delegate or explicitly exclude the cells you want to have no action if you do implement it.

More info here and here

Ios – What’s the difference between the atomic and nonatomic attributes

The last two are identical; "atomic" is the default behavior (~~note that it is not actually a keyword; it is specified only by the absence of nonatomic~~ -- atomic was added as a keyword in recent versions of llvm/clang).

Assuming that you are @synthesizing the method implementations, atomic vs. non-atomic changes the generated code. If you are writing your own setter/getters, atomic/nonatomic/retain/assign/copy are merely advisory. (Note: @synthesize is now the default behavior in recent versions of LLVM. There is also no need to declare instance variables; they will be synthesized automatically, too, and will have an _ prepended to their name to prevent accidental direct access).

With "atomic", the synthesized setter/getter will ensure that a whole value is always returned from the getter or set by the setter, regardless of setter activity on any other thread. That is, if thread A is in the middle of the getter while thread B calls the setter, an actual viable value -- an autoreleased object, most likely -- will be returned to the caller in A.

In nonatomic, no such guarantees are made. Thus, nonatomic is considerably faster than "atomic".

What "atomic" does not do is make any guarantees about thread safety. If thread A is calling the getter simultaneously with thread B and C calling the setter with different values, thread A may get any one of the three values returned -- the one prior to any setters being called or either of the values passed into the setters in B and C. Likewise, the object may end up with the value from B or C, no way to tell.

Ensuring data integrity -- one of the primary challenges of multi-threaded programming -- is achieved by other means.

Adding to this:

atomicity of a single property also cannot guarantee thread safety when multiple dependent properties are in play.

Consider:

 @property(atomic, copy) NSString *firstName;
 @property(atomic, copy) NSString *lastName;
 @property(readonly, atomic, copy) NSString *fullName;

In this case, thread A could be renaming the object by calling setFirstName: and then calling setLastName:. In the meantime, thread B may call fullName in between thread A's two calls and will receive the new first name coupled with the old last name.

To address this, you need a transactional model. I.e. some other kind of synchronization and/or exclusion that allows one to exclude access to fullName while the dependent properties are being updated.

Best Answer

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