关于 ReactiveCocoa，首先需要了解三个概念：map，filter 和 fold。
One of the key concepts of functional programming is that of a “higher-order function”.
Accordingto Wikipedia, a higher-order function is a function that satisfies these two conditions:
? It takes one or more functions as input.
? It outputs a function.
In Objective-C, we often use blocks as functions.
Use CocoaPods to install RXCollections in your project. In your application:didFinishLaunchingWithOptions: method，do some code,create the array first.
NSArray *array =@[@(1),@(2),@(3)];
map(1,2,3)=>(1,4,9)
using RXCollections：
//map
NSArray *mappedArray = [array rx_mapWithBlock:^id(id each) {
return @(pow([each integerValue], 2));
}];
NSLog(@"%@",mappedArray);
NSMutableArray *mutableArray = [NSMutableArray arrayWithCapacity:array.count];
for (NSNumber *number in array) {
[mutableArray addObject:@(pow([number integerValue], 2))];
}
NSArray *mappedArray = [NSArray arrayWithArray:mutableArray];Filtering a list just returns a new list containing all of the original entries,
minus the entries that didn’t return true from a test.
using RXCollections：
//filter
NSArray *filteredArray = [array rx_filterWithBlock:^BOOL(id each) {
return ([each integerValue]%2 == 0);
}];
NSLog(@"%@",filteredArray);
NSMutableArray *mutableArray = [NSMutableArray arrayWithCapacity:array.count];
for (NSNumber *number in array) {
if ([number integerValue]%2 == 0) {
[mutableArray addObject:number];
}
}
NSArray *filteredArray = [NSArray arrayWithArray:mutableArray];
A simple fold can be used to combine the integer values of each member of our array to calculate their sum.
//fold
NSNumber *sum = [array rx_foldWithBlock:^id(id memo, id each) {
//memo : return value of the previous invocation of the block (the initial value is nil).
return @([memo integerValue] + [each integerValue]);
}];
NSLog(@"%@",sum);
[[array rx_mapWithBlock:^id(id each) {
return [each stringValue];
}] rx_foldInitialValue:@"" block:^id(id memo, id each) {
return [memo stringByAppendingString:[each stringValue]];
}];you can NSLog，is @“123”.
We also saw, in the last example, how we can chain operations together to get a more complex result.
In fact,chaining operations together is one of the main principles of using ReactiveCocoa.
ReactiveCocoa (2) map,filter,fold,布布扣,bubuko.com
ReactiveCocoa (2) map,filter,fold
原文：http://blog.csdn.net/crayondeng/article/details/20302743