34、开发应用程序与iOS开发差异解析

开发应用程序与iOS开发差异解析

开发应用程序相关代码与操作

在开发应用程序时，首先需要设置排序描述符。以下是相关代码：

// setup the sort descriptors 
// remember to trigger KVO notifications so the relevant controllers can be 
//  updated-- they’re already bound by this point 
if ( _personSortDescriptors == nil ) 
{ 
    [self willChangeValueForKey: @"personSortDescriptors"]; 
    _personSortDescriptors = @[[NSSortDescriptor sortDescriptorWithKey: @"lastName" 
                                                             ascending: YES]]; 
    [self didChangeValueForKey: @"personSortDescriptors"]; 
} 
if ( _labelSortDescriptors == nil ) 
{ 
    [self willChangeValueForKey: @"labelSortDescriptors"]; 
    _labelSortDescriptors = @[[NSSortDescriptor sortDescriptorWithKey: @"label"