通过 NSInvocation 间接调用对象的方法

Mediator.m

#import "Mediator.h"

NSString * const kMediatorParamsKeySwiftTargetModuleName = @"kMediatorParamsKeySwiftTargetModuleName";


@interface Mediator ()

@property (nonatomic, copy) NSMutableDictionary *cachedTarget;

@end

@implementation Mediator

+ (instancetype)sharedInstance {
    static Mediator *mediator;
    static dispatch_once_t token;
    dispatch_once(&token, ^{
        mediator = [[Mediator alloc] init];
    });
    
    return mediator;
}

- (id)performActionWithUrl:(NSURL *)url completion:(void (^)(NSDictionary *))completion {
    NSMutableDictionary *params = [NSMutableDictionary dictionary];
    NSString *urlString = [url query];
    
    for (NSString * params in [urlString componentsSeparatedByString:@"&"]) {
        NSArray *elements = [params componentsSeparatedByString:@"="];
        if (elements.count <2) {
            continue;
        }
        
        [params setValue:elements.lastObject forKey:elements.firstObject];
    }
    
    NSString *actionName = [url.path stringByReplacingOccurrencesOfString:@"/" withString:@""];
    if ([actionName hasPrefix:@"native"]) {
        return @(NO);
    }
    
    id result = [self performTarget:url.host action:actionName params:params shouldCacheTarget:NO];
    if (completion && result) {
        completion(@{@"reuslt": result});
    } else {
        completion(nil);
    }
    return result;
}

- (id)performTarget:(NSString *)targetName action:(NSString *)actionName params:(NSDictionary *)params shouldCacheTarget:(BOOL)shouldCacheTarget {
    
    NSString *swiftModuleName = params[kMediatorParamsKeySwiftTargetModuleName];
    
    // 1、创建 targetClassName
    NSString *targetClassName;
    if (swiftModuleName.length > 0) {
        targetClassName = [NSString stringWithFormat:@"%@.Target_%@", swiftModuleName, targetName];
    } else {
        targetClassName = [NSString stringWithFormat:@"Target_%@", targetName];
    }
    
    NSObject *target = self.cachedTarget[targetClassName];
    if (target == nil) {
        // 2、创建 targetClass
        Class targetClass = NSClassFromString(targetClassName);
        // 3、创建 target
        target = [[targetClass alloc] init];
    }
    
    if (shouldCacheTarget) {
        self.cachedTarget[targetClassName] = target;
    }
    
    // 4、创建 actionString
    NSString *actionString = [NSString stringWithFormat:@"Action_%@", actionName];
    // 5、创建 selector
    SEL selctor = NSSelectorFromString(actionString);
    
    if ([target respondsToSelector:selctor]) {
        return [self safePerformAction:target action:selctor params:params];
    } else {
        return nil;
    }
}



- (id)safePerformAction:(NSObject *)target action:(SEL)action params:(NSDictionary *) params {
    // 6、创建 methodSignature
    NSMethodSignature *methodSignature = [target methodSignatureForSelector:action];
    if (methodSignature == nil) {
        return nil;
    }
    
    // 7、创建 returnType
    const char* returnType = [methodSignature methodReturnType];
    
    if (strcmp(returnType, @encode(void)) == 0) {
        // 8、创建 invocation
        NSInvocation *invocation = [NSInvocation invocationWithMethodSignature:methodSignature];
        [invocation setArgument:&params atIndex:2];
        [invocation setTarget:target];
        [invocation setSelector:action];
       
        [invocation invoke];
        
        return nil;
    }
    
    if (strcmp(returnType, @encode(BOOL)) == 0) {
        NSInvocation *invocation = [NSInvocation invocationWithMethodSignature:methodSignature];
        [invocation setTarget:target];
        [invocation setSelector:action];
        [invocation setArgument:&params atIndex:2];
        [invocation invoke];
        
        BOOL result = 0;
        [invocation getReturnValue:&result];
        return @(result);
    }
    
    if (strcmp(returnType, @encode(CGFloat)) == 0) {
        NSInvocation *invocation = [NSInvocation invocationWithMethodSignature:methodSignature];
        [invocation setTarget:target];
        [invocation setSelector:action];
        [invocation setArgument:&params atIndex:2];
        [invocation invoke];
        
        CGFloat result = 0;
        [invocation getReturnValue:&result];
        return @(result);
    }
    
    if (strcmp(returnType, @encode(NSInteger)) == 0) {
        NSInvocation *invocation = [NSInvocation invocationWithMethodSignature:methodSignature];
        [invocation setTarget:target];
        [invocation setSelector:action];
        [invocation setArgument:&params atIndex:2];
        [invocation invoke];
        
        NSInteger result = 0;
        [invocation getReturnValue:&result];
        return @(result);
    }
    
    if (strcmp(returnType, @encode(NSUInteger)) == 0) {
        NSInvocation *invocation = [NSInvocation invocationWithMethodSignature:methodSignature];
        [invocation setTarget:target];
        [invocation setSelector:action];
        [invocation setArgument:&params atIndex:2];
        [invocation invoke];
        
        NSUInteger result = 0;
        [invocation getReturnValue:&result];
        return @(result);
    }

#pragma clang diagnostic push
#pragma clang diagnostic ignored "-Warc-performSelector-leaks"
    return [target performSelector:action withObject:params];
#pragma cland diagnostic pop
}

- (void)releaseCachedTargetWithTargetName:(NSString *)targetName {
    NSString *key = [NSString stringWithFormat:@"Target_%@",targetName];
    [self.cachedTarget removeObjectForKey:key];
}

- (NSMutableDictionary *)cachedTarget{
    if (_cachedTarget == nil) {
        _cachedTarget = [NSMutableDictionary dictionary];
    }
    return _cachedTarget;
}

@end