核心数据NSPredicate检查BOOL值 [英] Core Data NSPredicate checking for BOOL value

问题描述

我目前有一个问题，从db从ie的所有数据参数为TRUE。

我使用 NSPredicate 下面是一个示例代码

  NSManagedObjectContext * context = managedObjectContext_; 
 
 if（！context）{
 //处理错误。 
 NSLog（@ERROR CONTEXT IS NIL）; 
} 
 
 NSEntityDescription * entity = [NSEntityDescription entityForName：@tblcontentinManagedObjectContext：managedObjectContext_]; 
 
 NSFetchRequest * request = [[NSFetchRequest alloc] init]; 
 
 NSPredicate * predicate = [NSPredicate predicateWithFormat：@bookmarked == YES]; 
 
 [request setPredicate：predicate]; 
 

我尝试将predicatewithformat设置为几乎所有内容，但它仍然不提取包含 YES 值。

我还试过了（@bookmarked ==％d，YES） / code>但没有运气。我不想得到整个数组，然后通过 if（object.bookmarked == YES） ..... blabla手动过滤它。

非常感谢。

解决方案

基于Apple Document 这里，我们可以使用以下两种方法来比较布尔值：

  NSPredicate * newPredicate = [NSPredicate predicateWithFormat ：@anAttribute ==％@，[NSNumber numberWithBool：aBool]]; 
 NSPredicate * testForTrue = [NSPredicate predicateWithFormat：@anAttribute == YES];但是，上面的谓词不能得到空的 anAttribute   
 code>。要处理空属性，您需要根据Apple文档 here ：
  predicate = [NSPredicate predicateWithFormat：@firstName = nil]; //它在文档
  
或
  predicate = [NSPredicate predicateWithFormat：@firstName == nil]; // ==和=在这里可以互换。
  
 
I am currently having an issue pulling all data from db whereby i.e 1 parameter is TRUE.

I am using NSPredicate and below is a sample code
NSManagedObjectContext *context = managedObjectContext_;

if (!context) {
    // Handle the error.
    NSLog(@"ERROR CONTEXT IS NIL");
}

NSEntityDescription *entity = [NSEntityDescription entityForName:@"tblcontent" inManagedObjectContext:managedObjectContext_];

NSFetchRequest *request = [[NSFetchRequest alloc] init];

NSPredicate *predicate = [NSPredicate predicateWithFormat:@"bookmarked == YES"];

[request setPredicate:predicate];
I tried setting predicatewithformat to almost everything but it still does not pull out bookmarks which have a YES value.

I even tried (@"bookmarked == %d",YES) but with not luck. I don't want to have to get the whole array and then filter it manually by doing if(object.bookmarked == YES) .....blabla.

I will really appreciate some help.

Many thanks.
解决方案
Based on Apple Document Here, we can use the following two methods to compare Boolean:
NSPredicate *newPredicate = [NSPredicate predicateWithFormat:@"anAttribute == %@",[NSNumber numberWithBool:aBool]];
NSPredicate *testForTrue = [NSPredicate predicateWithFormat:@"anAttribute == YES"];
However, the above predicate cannot get out the ones with empty anAttribute. To deal with an empty attribute, you need the following method according to Apple document here:
predicate = [NSPredicate predicateWithFormat:@"firstName = nil"]; // it's in the document
or
predicate = [NSPredicate predicateWithFormat:@"firstName == nil"]; // == and = are interchangeable here


                        
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