IOS Crash Issue warning error 2

Capturing ' self ' strongly in this block are likely to leads to a retain cycle

__block Viewcontroller *controller = self;
[_tableview setpulltorefreshhandler:^{
[Controller Datadidrefresh:nil];
}];

The _block tag tells the compiler that this variable needs special handling in the block.

In general, the value of the variable used in the block is copied, so the modification of the variable itself does not affect the actual value of the variable. And when we mark it with __block, it means that the change in the block is also effective outside the block.

IOS Crash Issue warning error 2