[英]Filter an Array of Dictionaries by using a Predicate
I have the following array of dictionaries: 我有以下几本字典:
Printing description of newOrderbookBids:
<__NSArrayI 0x10053e7c0>(
{
price = "10.14";
size = 148;
},
{
price = "10.134";
size = 0;
},
{
price = "10.131";
size = 321;
})
Each dictionary in the array has the keys price
and size
, both are numbers. 数组中的每个字典都有键price
和size
,它们都是数字。
I would like to return a filtered array which contains only the dictionaries for which size > 0
. 我想返回一个仅包含size > 0
的字典的过滤数组。 In this example, this would be the array with dictionary #1 and #3, but without dictionary #2: 在此示例中,这将是具有字典#1和#3但没有字典#2的数组:
({
price = "10.14";
size = 148;
},
{
price = "10.131";
size = 321;
})
I have tried the following code snippet to filter my NSArray *newOrderbookBids
by size: 我尝试了以下代码片段按大小过滤我的NSArray *newOrderbookBids
:
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"size > 0"];
newOrderbookBids = [newOrderbookBids filteredArrayUsingPredicate:predicate];
Unfortunately my code crashes with the runtime error 不幸的是,我的代码因运行时错误而崩溃
[NSSymbolicExpression compare:]: unrecognized selector sent to instance xxxx
What is wrong with my code and predicate? 我的代码和谓词有什么问题? How can I filter by size > 0
? 如何按size > 0
过滤?
Thank you! 谢谢!
"SIZE" is a reserved keyword in the "Predicate Format String Syntax" and the keywords are case-insensitive. “ SIZE”是“谓词格式字符串语法”中的保留关键字,并且该关键字不区分大小写。
To solve that problem, use the "%K" format argument as a var arg substitution for a key path : 要解决该问题,请使用“%K”格式参数作为键路径的var arg替代:
NSPredicate *predicate = [NSPredicate predicateWithFormat:@"%K > 0", @"size"];
Reserved Words 保留字
The following words are reserved: 以下是保留字:
AND, OR, IN, NOT, ALL, ANY, SOME, NONE, LIKE, CASEINSENSITIVE, CI, MATCHES, CONTAINS, BEGINSWITH, ENDSWITH, BETWEEN, NULL, NIL, SELF, TRUE, YES, FALSE, NO, FIRST, LAST, SIZE, ANYKEY, SUBQUERY, CAST, TRUEPREDICATE, FALSEPREDICATE 并且,或者,不是(不是)所有,任何,某些,无,类似,不区分大小写,CI,匹配,包含,开头,结尾,介于,NULL,NIL,自我,TRUE,YES,FALSE,NO,FIRST,LAST,LAST,大小,任意键,子查询,投射,真伪,伪伪
A clearer error message when this happens would be nice. 发生这种情况时,更清晰的错误消息会很好。
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