为Objective-C提供LINQ风格的查询接口：LINQ4Obj-C
LINQ4Obj-C为为Objective-C提供LINQ风格的流畅查询接口。该项目为Objective-C带来了LINQ标准查询操作。This is achieved by collection of categories for NSArray and NSDictionary classes。
Aggregate
对集合的值执行自定义聚合运算。
- (id)linq_aggregate:(LINQAccumulatorBlock)accumulatorBlock; The following example creates a coma-separated string from an array of strings.
NSArray *input = @[@"M", @"A", @"R", @"K"]; NSString *result = [input linq_aggregate:^id(id item, id aggregate) { return [NSString stringWithFormat:@"%@, %@", aggregate, item]; }]; // Result is: @"M, A, R, K" Average
Calculates the average value of a collection of values.
- (id)linq_avg; Calculates the average value of the attribute specified by the key parameter for all objects in the collection.
- (id)linq_avgForKey:(NSString *)key; Example: Return the average length of strings in the collection.
NSArray *words = @[@"A", @"AB", @"ABC", @"ABCD", @"ABCDE"]; NSNumber *avg_word_length = [words linq_avgForKey:@"length"]; // Result is 3.
Count
Counts the elements in a collection, optionally only those elements that satisfy a predicate function.
- (NSUInteger)linq_count:(LINQConditionBlock)conditionBlock; Example: Return the number of elements in the collection that are not smaller than 8.
NSArray *numbers = [NSArray linq_from:1 to:10]; NSInteger *count = [numbers linq_count:^BOOL(id item) { return ([item compare:@8] != NSOrderedAscending); }]; // Count is 3. Max
Determines the maximum value in a collection.
- (id)linq_max; Calculates the max value of the attribute specified by the key parameter for all objects in a collection.
- (id)linq_maxForKey:(NSString *)key;- Min
Determines the minimum value in a collection.
- (id)linq_min; Calculates the min value of the attribute specified by the key parameter for all objects in the collection.
- (id)linq_minForKey:(NSString *)key; Sum
Calculates the sum of the values in a collection.
- (id)linq_sum; Calculates the sum of values of the attribute specified by the key parameter for all objects in a collection.
- (id)linq_sumForKey:(NSString *)key; Converting Operations
ToArray
Puts value elements into an NSArray.
- (NSArray *)linq_toArray; Puts value elements into a NSArray which satisfy key condtion.
- (NSArray *)linq_toArrayWhereKey:(LINQConditionBlock)conditionBlock; Puts value elements into a NSArray which satisfy value condtion.
- (NSArray *)linq_toArrayWhereValue:(LINQConditionBlock)conditionBlock; Puts value elements into a NSArray which satisfy both key and value condtion.
- (NSArray *)linq_toArrayWhereKeyValue:(LINQKeyValueConditionBlock)conditionBlock; ToDictionary
Puts elements into an index-key-based NSDictionary.
- (NSDictionary *)linq_toDictionary; Puts elements into a NSDictionary based on a key selector function.
- (NSDictionary *)linq_toDictionaryWithKeySelector:(LINQSelectorBlock)keySelector; Puts elements into a NSDictionary based on a key and value selector functions.
- (NSDictionary *)linq_toDictionaryWithKeySelector:(LINQSelectorBlock)keySelector valueSelector:(LINQSelectorBlock)valueSelector; Filtering Operations
OfType
Selects values, depending on their ability to be cast to a specified type.
- (instancetype)linq_ofType:(Class)klass; Selects elements which keys can be cast to a specified type.
- (instancetype)linq_ofTypeKey:(Class)klass; Selects elements which values can be cast to a specified type.
- (instancetype)linq_ofTypeValue:(Class)klass; Where
Selects values that are based on a predicate function.
- (instancetype)linq_where:(LINQConditionBlock)conditionBlock; Selects values which satisify key-value condition.
- (instancetype)linq_where:(LINQKeyValueConditionBlock)conditionBlock; Selects values which keys satisify condition.
- (instancetype)linq_whereKey:(LINQConditionBlock)conditionBlock; Selects values which satisify condition.
- (instancetype)linq_whereValue:(LINQConditionBlock)conditionBlock; Generation Operations
Empty
Returns empty array.
+ (instancetype)linq_empty; From:To:
Creates array with integers from to.
+ (instancetype)linq_from:(NSInteger)from to:(NSInteger)to; Repeat
Generates a collection that contains one repeated value.
+ (instancetype)linq_repeat:(id)element count:(NSInteger)count; Grouping Operations
GroupBy
Returns NSDictionary of groups that share a common attribute defined by selector. Each group is defined as a dictionary entry whose key is a result of a selector and its value is an array of all elements that return the same key, i.e. selector(element) -> key.
{ key <- selector(element), value <- [element : key = selector(element)] }
- (NSDictionary *)linq_groupBy:(LINQSelectorBlock)selector; Example:
NSArray *words = @[@"Adam", @"Anthony", @"Ben", @"Bob", @"Michael", @"Max", @"Matt", @"Simon"]; NSDictionary *results = [self.input_words linq_groupBy:^id(id item) { return [item substringToIndex:1]; }]; // Result is: // { // {"A" : @[@"Adam", @"Anthony"]}, // {"B" : @[@"Ben", @"Bob"]}, // {"M" : @[@"Michael", @"Max", @"Matt"]} // {"S" : @[@"Simon"]} // } ToLookup
Returns array of NSDictionaries by entering each element into a NSDictionary whose key is a result of a selector and its value is an element: { key <- selector(element), value <- element}
- (instancetype)linq_toLookup:(LINQSelectorBlock)selector; Lookup
Helps to filter results of toLookup: method. Returns array of NSDictionaries with the same key.
- (instancetype)linq_lookup:(id)key; Partitioning Operations
Skip
Skips elements up to a specified position in a collection.
- (NSArray *)linq_skip:(NSInteger)count; - (NSDictionary *)linq_skip:(NSInteger)count; Take
Takes elements up to a specified position in a collection.
- (NSArray *)linq_take:(NSInteger)count; - (NSDictionary *)linq_take:(NSInteger)count; Projection Operations
Select
Projects values that are based on a transform function.
- (instancetype)linq_select:(LINQSelectorBlock)selectorBlock; The example below adds 10 to each element in the collection.
NSArray *result = [[NSArray linq_from:1 to:5] linq_select:^id(id item) { return [NSNumber numberWithInteger:([item integerValue] + 10)]; }]; // result is @[@11, @12, @13, @14, @15]; Select Many
Projects sequences of values that are based on a transform function and then flattens them into one sequence.
- (instancetype)linq_selectMany:(LINQSelectorBlock)selectorBlock; This example returns words of each string of the collection.
NSArray *input = @[@"an apple a day", @"the quick brown fox"]; NSArray *result = [input linq_selectMany:^id(id item) { return [item componentsSeparatedByString:@" "]; }]; // result is @[@"an", @"apple", @"a", @"day", // @"the", @"quick", @"brown", @"fox"] // Quantifier Operations
All
Determines whether all the elements in a sequence satisfy a condition.
- (BOOL)linq_all:(LINQConditionBlock)conditionBlock; - (BOOL)linq_all:(LINQKeyValueConditionBlock)conditionBlock; Any
Determines whether any elements in a sequence satisfy a condition.
- (BOOL)linq_any:(LINQConditionBlock)conditionBlock; - (BOOL)linq_any:(LINQKeyValueConditionBlock)conditionBlock; Set Operations
Distinct
Removes duplicate values from a collection.
- (instancetype)linq_distinct; Except
Returns the collection without the elements that appear in a second collection.
- (instancetype)linq_except:(NSArray *)other; - (instancetype)linq_except:(NSDictionary *)other; Intersect
Returns the set intersection, which means elements that appear in each of two collections.
- (instancetype)linq_intersect:(NSArray *)other; - (instancetype)linq_intersect:(NSDictionary *)other; Union
Returns the set union, which means unique elements that appear in either of two collections.
- (NSArray *)linq_union:(NSArray *)other; Merges to dictionaries by returning the set union of unique elements which keys appear in either of two dictionaries.
- (NSDictionary *)linq_merge:(NSDictionary *)other; Sorting Operations
OrderBy
Sorts values in ascending order.
- (instancetype)linq_orderByAscending; Sorts values in descending order.
- (instancetype)linq_orderByDescending; Sorts elements of a collection depending on an element's key.
- (instancetype)linq_orderByKey:(NSString *)key ascending:(BOOL)ascending; Reverse
Reverses the order of the elements in a collection.
- (instancetype)linq_reverse;