Xcode NSPredicate

Question

我正在尝试过滤对象数组，如下所示：

{
    "id": "0",
    "title": "Crucifix and sarcophagus of Ariberto da Intimiano",
    "categoryName": "COMMEMORATIVE MONUMENTS",
    "audioFile": "Crucifix-and-sarcophagus-of-Ariberto-da-Intimiano",
    "videoFile": null,
    "textFile": "Crucifix-and-sarcophagus-of-Ariberto-da-Intimiano",
    "image": "content/0/Crucifix-and-sarcophagus-of-Ariberto-da-Intimiano_flow.jpg",
    "numPictures": "1",
    "didascalie": ["dida 1", "dida 2", "dida 3"],
    "description": "Crucifix and sarcophagus of Ariberto da Intimiano",
    "link": ""
},
{
    "id": "1",
    "title": "The sundial of Duomo",
    "categoryName": "THE SUNDIAL",
    "audioFile": "The-sundial-of-Duomo",
    "videoFile": null,
    "textFile": "The-sundial-of-Duomo",
    "image": "content/1/The-sundial-of-Duomo_flow.jpg",
    "numPictures": "2",
    "didascalie": ["dida 1", "dida 2", "dida 3"],
    "description": "The sundial of Duomo",
    "link": ""
}


NSPredicate *key1Predicate = [NSPredicate predicateWithFormat:@"title == '%@'",_searchAZ.text];

    _ArtWorksTableResults = [[_ArtWorksTable filteredArrayUsingPredicate:key1Predicate] mutableCopy];

    NSLog(@"%i",_ArtWorksTableResults.count);

当我执行搜索时，_ArtWorksTableResults.count总是0。

但如果我编写谓词而不是使用搜索栏文本，如下所示：

NSPredicate *key1Predicate = [NSPredicate predicateWithFormat:@"title == 'The sundial of duomo'"];

    _ArtWorksTableResults = [[_ArtWorksTable filteredArrayUsingPredicate:key1Predicate] mutableCopy];

    NSLog(@"%i",_ArtWorksTableResults.count);

_ArtWorksTableResults.count是1，这是正确的！

我做错了什么？

我还尝试记录搜索栏文本，一切正常。

我不明白为什么如果我直接在代码中写搜索的关键字就行了！

Answer 1

当您提供参数时，您的谓词格式中不应包含引号：

[NSPredicate predicateWithFormat:@"title == %@",_searchAZ.text];

Answer 2

https://developer.apple.com/library/mac/documentation/Cocoa/Conceptual/Predicates/Articles/pCreating.html

不需要额外的‘符号，它们是由格式化程序添加的

最后：

@"%K == '%@'"
This predicate checks whether the value of the key %K is equal to the string literal “%@“ (note the single quotes around %@). The key name %K is supplied at runtime as an argument to predicateWithFormat:.