react-native/React/Modules/RCTEventEmitter.m

99 lines
2.5 KiB
Objective-C

/**
* Copyright (c) Facebook, Inc. and its affiliates.
*
* This source code is licensed under the MIT license found in the
* LICENSE file in the root directory of this source tree.
*/
#import "RCTEventEmitter.h"
#import "RCTAssert.h"
#import "RCTUtils.h"
#import "RCTLog.h"
@implementation RCTEventEmitter
{
NSInteger _listenerCount;
}
+ (NSString *)moduleName
{
return @"";
}
+ (void)initialize
{
if (self != [RCTEventEmitter class]) {
RCTAssert(RCTClassOverridesInstanceMethod(self, @selector(supportedEvents)),
@"You must override the `supportedEvents` method of %@", self);
}
}
- (NSArray<NSString *> *)supportedEvents
{
return nil;
}
- (void)sendEventWithName:(NSString *)eventName body:(id)body
{
RCTAssert(_bridge != nil, @"Error when sending event: %@ with body: %@. "
"Bridge is not set. This is probably because you've "
"explicitly synthesized the bridge in %@, even though it's inherited "
"from RCTEventEmitter.", eventName, body, [self class]);
if (RCT_DEBUG && ![[self supportedEvents] containsObject:eventName]) {
RCTLogError(@"`%@` is not a supported event type for %@. Supported events are: `%@`",
eventName, [self class], [[self supportedEvents] componentsJoinedByString:@"`, `"]);
}
if (_listenerCount > 0) {
[_bridge enqueueJSCall:@"RCTDeviceEventEmitter"
method:@"emit"
args:body ? @[eventName, body] : @[eventName]
completion:NULL];
} else {
RCTLogWarn(@"Sending `%@` with no listeners registered.", eventName);
}
}
- (void)startObserving
{
// Does nothing
}
- (void)stopObserving
{
// Does nothing
}
- (void)dealloc
{
if (_listenerCount > 0) {
[self stopObserving];
}
}
RCT_EXPORT_METHOD(addListener:(NSString *)eventName)
{
if (RCT_DEBUG && ![[self supportedEvents] containsObject:eventName]) {
RCTLogError(@"`%@` is not a supported event type for %@. Supported events are: `%@`",
eventName, [self class], [[self supportedEvents] componentsJoinedByString:@"`, `"]);
}
_listenerCount++;
if (_listenerCount == 1) {
[self startObserving];
}
}
RCT_EXPORT_METHOD(removeListeners:(double)count)
{
int currentCount = (int)count;
if (RCT_DEBUG && currentCount > _listenerCount) {
RCTLogError(@"Attempted to remove more %@ listeners than added", [self class]);
}
_listenerCount = MAX(_listenerCount - currentCount, 0);
if (_listenerCount == 0) {
[self stopObserving];
}
}
@end