// Parses the predicate and attempts to generate a characteristic-value tuple.
static Tuple <HMCharacteristic, NSCopying> GetCharacteristicPair(this NSPredicate self)
{
var predicate = self as NSCompoundPredicate;
if (predicate == null)
{
return(null);
}
var subpredicates = predicate.Subpredicates;
if (subpredicates == null)
{
return(null);
}
if (subpredicates.Length != 2)
{
return(null);
}
NSComparisonPredicate characteristicPredicate = null;
NSComparisonPredicate valuePredicate = null;
foreach (var subpredicate in subpredicates)
{
var comparison = subpredicate as NSComparisonPredicate;
if (comparison != null && comparison.LeftExpression.ExpressionType == NSExpressionType.KeyPath && comparison.RightExpression.ExpressionType == NSExpressionType.ConstantValue)
{
var keyPath = comparison.LeftExpression.KeyPath;
if (keyPath == HMCharacteristic.KeyPath)
{
characteristicPredicate = comparison;
}
else if (keyPath == HMCharacteristic.ValueKeyPath)
{
valuePredicate = comparison;
}
}
}
if (characteristicPredicate != null && valuePredicate != null)
{
var characteristic = characteristicPredicate.RightExpression.ConstantValue as HMCharacteristic;
var characteristicValue = valuePredicate.RightExpression.ConstantValue as NSCopying;
return(new Tuple <HMCharacteristic, NSCopying> (characteristic, characteristicValue));
}
return(null);
}
private NSCompoundPredicate FindMatches(string searchString)
{
/*
* Each searchString creates an OR predicate for: name, yearIntroduced, introPrice.
* Example if searchItems contains "Gladiolus 51.99 2001":
* - name CONTAINS[c] "gladiolus"
* - name CONTAINS[c] "gladiolus", yearIntroduced ==[c] 2001, introPrice ==[c] 51.99
* - name CONTAINS[c] "ginger", yearIntroduced ==[c] 2007, introPrice ==[c] 49.98
*/
var searchItemsPredicate = new List <NSPredicate>();
/*
* Below we use NSExpression represent expressions in our predicates.
* NSPredicate is made up of smaller, atomic parts:
* two NSExpressions (a left-hand value and a right-hand value).
*/
// Name field matching.
var titleExpression = NSExpression.FromKeyPath(ExpressionKeys.Title);
var searchStringExpression = NSExpression.FromConstant(new NSString(searchString));
var titleSearchComparisonPredicate = new NSComparisonPredicate(titleExpression,
searchStringExpression,
NSComparisonPredicateModifier.Direct,
NSPredicateOperatorType.Contains,
NSComparisonPredicateOptions.CaseInsensitive | NSComparisonPredicateOptions.DiacriticInsensitive);
searchItemsPredicate.Add(titleSearchComparisonPredicate);
var numberFormatter = new NSNumberFormatter
{
NumberStyle = NSNumberFormatterStyle.None,
FormatterBehavior = NSNumberFormatterBehavior.Default
};
// The `searchString` may fail to convert to a number.
var targetNumber = numberFormatter.NumberFromString(searchString);
if (targetNumber != null)
{
// Use `targetNumberExpression` in both the following predicates.
var targetNumberExpression = NSExpression.FromConstant(targetNumber);
// The `yearIntroduced` field matching.
var yearIntroducedExpression = NSExpression.FromKeyPath(ExpressionKeys.YearIntroduced);
var yearIntroducedPredicate = new NSComparisonPredicate(yearIntroducedExpression,
targetNumberExpression,
NSComparisonPredicateModifier.Direct,
NSPredicateOperatorType.EqualTo,
NSComparisonPredicateOptions.CaseInsensitive | NSComparisonPredicateOptions.DiacriticInsensitive);
searchItemsPredicate.Add(yearIntroducedPredicate);
// The `price` field matching.
var priceExpression = NSExpression.FromKeyPath(ExpressionKeys.IntroPrice);
var finalPredicate = new NSComparisonPredicate(priceExpression,
targetNumberExpression,
NSComparisonPredicateModifier.Direct,
NSPredicateOperatorType.EqualTo,
NSComparisonPredicateOptions.CaseInsensitive | NSComparisonPredicateOptions.DiacriticInsensitive);
searchItemsPredicate.Add(finalPredicate);
}
return(NSCompoundPredicate.CreateOrPredicate(searchItemsPredicate.ToArray()));
}
