iOS Learning (errors encountered in Project 1)

1.[appmodel Copywithzone:]: Unrecognized selector sent to instance 0x7ffda9f4cf70

Terminating app due to uncaught exception ' nsinvalidargumentexception ', Reason: '-[appmodel copywithzone:]: Unrecogni Zed Selector sent to instance 0x7ffda9f4cf70 '

First throw Call stack:

The cause of this error: The problem with attribute definitions should be noted when defining a property

Some problems may occur when the property

Nonatomic: Single thread, high efficiency

Atomic: Multithreading, low efficiency benefits, but default

readWrite: Readable and writable, it is also the default

ReadOnly: Readable only

Assign: Refers to the int,float. Equal value type, he is the default

Copy: Refers to a String object. such as name

Retain: Refers to an object. such as time objects

Strong: Strong references

Weak: Weak references

The reason I went wrong is that when I define a class object, I misuse copy instead of strong

2. when using TableView , it will be found that sometimes this method does not execute, Reason:_tableview frame is not set, there is _dataarry An unassigned value is empty. There is also the use of the data in the asynchronous way, but the wood has to refresh the TableView data

-(uitableviewcell *) TableView: (uitableview *) TableView Cellforrowatindexpath: (Nsindexpath *) indexpath{

return nil;

}

3. Data NSData errors caused by uninitialized initialization

Terminating app due to uncaught exception ' nsinvalidargumentexception ', Reason: ' Data parameter is nil '

4. If the extracted data is empty, the following error will occur

Terminating app due to uncaught exception ' nsrangeexception ', Reason: ' * * *-[__nsarraym Objectatindex:]: Index 3 Beyon D bounds [0.. 2] '

Copyright NOTICE: This article for Bo Master original article, without Bo Master permission not reproduced.

iOS Learning (errors encountered in Project 1)