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()));
}
static NSPredicate ToPredicate(NSObject @object)
{
if (@object == NSNumber.FromBoolean(true))
{
return(NSPredicate.FromValue(true));
}
if (@object == NSNumber.FromBoolean(false))
{
return(NSPredicate.FromValue(false));
}
if (@object is NSArray == false)
{
return(null);
}
var array = (NSArray)@object;
var objects = SubArray(array);
var op = objects[0].ToString();
if (MGLPredicateOperatorTypesByJSONOperator.TryGetValue(op, out var operatorType))
{
NSComparisonPredicateOptions options = 0;
if (objects.Count > 3)
{
var collatorExpression = SubArray((NSArray)objects[3]);
if (collatorExpression.Count != 2)
{
return(null);
}
var collator = (NSDictionary)collatorExpression[1];
if (false == collator.ContainsKey((NSString)"locale"))
{
if (collator.ValueForKey((NSString)"case-sensitive") == NSNumber.FromBoolean(false))
{
options |= NSComparisonPredicateOptions.CaseInsensitive;
}
if (collator.ValueForKey((NSString)"diacritic-sensitive") == NSNumber.FromBoolean(false))
{
options |= NSComparisonPredicateOptions.DiacriticInsensitive;
}
}
}
var subexpressions = ToSubexpressions(SubArray(objects, 1));
return(new NSComparisonPredicate(
subexpressions[0],
subexpressions[1],
NSComparisonPredicateModifier.Direct,
operatorType,
options
));
}
switch (op)
{
case "!": {
var subpredicates = ToSubpredicates(SubArray(objects, 1));
if (subpredicates.Count > 1)
{
var predicate = NSCompoundPredicate.CreateOrPredicate(subpredicates.ToArray());
return(NSCompoundPredicate.CreateNotPredicate(predicate));
}
return(NSPredicate.FromValue(true));
}
case "all": {
var subpredicates = ToSubpredicates(SubArray(objects, 1));
if (subpredicates.Count == 2)
{
if (subpredicates[0] is NSComparisonPredicate leftCondition &&
subpredicates[1] is NSComparisonPredicate rightCondition
)
{
NSExpression[] limits = null;
NSExpression leftConditionExpression = null;
if (leftCondition.PredicateOperatorType == NSPredicateOperatorType.GreaterThanOrEqualTo &&
rightCondition.PredicateOperatorType == NSPredicateOperatorType.LessThanOrEqualTo
)
{
limits = new NSExpression[]
{
leftCondition.RightExpression,
rightCondition.RightExpression
};
leftConditionExpression = leftCondition.LeftExpression;
}
else if (leftCondition.PredicateOperatorType == NSPredicateOperatorType.LessThanOrEqualTo &&
rightCondition.PredicateOperatorType ==
NSPredicateOperatorType.LessThanOrEqualTo
)
{
limits = new NSExpression[]
{
leftCondition.LeftExpression,
rightCondition.RightExpression
};
leftConditionExpression = leftCondition.RightExpression;
}
else if (leftCondition.PredicateOperatorType == NSPredicateOperatorType.LessThanOrEqualTo &&
rightCondition.PredicateOperatorType ==
NSPredicateOperatorType.GreaterThanOrEqualTo
)
{
limits = new NSExpression[]
{
leftCondition.LeftExpression,
rightCondition.LeftExpression
};
leftConditionExpression = leftCondition.RightExpression;
}
else if (leftCondition.PredicateOperatorType == NSPredicateOperatorType.GreaterThanOrEqualTo &&
rightCondition.PredicateOperatorType ==
NSPredicateOperatorType.GreaterThanOrEqualTo
)
{
limits = new NSExpression[]
{
leftCondition.RightExpression,
rightCondition.LeftExpression
};
leftConditionExpression = leftCondition.LeftExpression;
}
if (limits != null && leftConditionExpression != null)
{
return(NSPredicate.FromFormat("%@ BETWEEN %@", leftConditionExpression,
NSExpression.FromAggregate(limits)));
}
}
}
return(new NSCompoundPredicate(NSCompoundPredicateType.And, subpredicates.ToArray()));
}
case "any": {
var subpredicates = ToSubpredicates(SubArray(objects, 1));
return(new NSCompoundPredicate(NSCompoundPredicateType.Or, subpredicates.ToArray()));
}
default: {
var expression = ToExpression(array);
return(new NSComparisonPredicate(
expression,
NSExpression.FromConstant(NSNumber.FromBoolean(true)),
NSComparisonPredicateModifier.Direct,
NSPredicateOperatorType.EqualTo,
0
));
}
}
}