如何检查用户的ios设备上是否安装了某些app？

1. 使用canOpenURL判断

NSURL *instagramURL = [NSURL URLWithString:@"instagram://location?id=1"];
BOOL hasInstagram = [[UIApplication sharedApplication] canOpenURL:instagramURL];

此方法需要定义URLSchemes

2. UIDevice Category For Processes

// .h

@interface UIDevice (ProcessesAdditions)
- (NSArray *)runningProcesses;
@end

// .m
#import <sys/sysctl.h>

@implementation UIDevice (ProcessesAdditions)

- (NSArray *)runningProcesses {

        int mib[4] = {CTL_KERN, KERN_PROC, KERN_PROC_ALL, 0};
        size_t miblen = 4;
        
        size_t size;
        int st = sysctl(mib, miblen, NULL, &size, NULL, 0);
        
        struct kinfo_proc * process = NULL;
        struct kinfo_proc * newprocess = NULL;
        
    do {
                
        size += size / 10;
        newprocess = realloc(process, size);
                
        if (!newprocess){
                        
            if (process){
                free(process);
            }
                        
            return nil;
        }
                
        process = newprocess;
        st = sysctl(mib, miblen, process, &size, NULL, 0);
                
    } while (st == -1 && errno == ENOMEM);
        
        if (st == 0){
                
                if (size % sizeof(struct kinfo_proc) == 0){
                        int nprocess = size / sizeof(struct kinfo_proc);
                
                        if (nprocess){
                        
                                NSMutableArray * array = [[NSMutableArray alloc] init];
        
                                for (int i = nprocess - 1; i >= 0; i--){
                
                                        NSString * processID = [[NSString alloc] initWithFormat:@"%d", process[i].kp_proc.p_pid];
                                        NSString * processName = [[NSString alloc] initWithFormat:@"%s", process[i].kp_proc.p_comm];
                
                                        NSDictionary * dict = [[NSDictionary alloc] initWithObjects:[NSArray arrayWithObjects:processID, processName, nil] 
                                                                                                                                                forKeys:[NSArray arrayWithObjects:@"ProcessID", @"ProcessName", nil]];
                                        [processID release];
                                        [processName release];
                                        [array addObject:dict];
                                        [dict release];
                                }
        
                                free(process);
                                return [array autorelease];
                        }
                }
        }
        
        return nil;
}

@end

// Example usage.
NSArray * processes = [[UIDevice currentDevice] runningProcesses];
for (NSDictionary * dict in processes){
        NSLog(@"%@ - %@", [dict objectForKey:@"ProcessID"], [dict objectForKey:@"ProcessName"]);
}