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Refactor DataController: deal with errors
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Also:
* make DataController more robust
* add better docs for it
* improved cache clearing method
* made code a little nicer to read
* learned a ton about blocks
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@cdzombak
cdzombak committed Feb 3, 2012
1 parent 9bbdc90 commit ba19714
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Showing 5 changed files with 181 additions and 105 deletions.
2 changes: 1 addition & 1 deletion CAENLabStatus/DZCAppDelegate.m
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Original file line number Diff line number Diff line change
Expand Up @@ -43,8 +43,8 @@ - (void)applicationWillResignActive:(UIApplication *)application
- (void)applicationDidBecomeActive:(UIApplication *)application
{
if (self.appWasInBackground) {
[self.dataController clearCache];
[self.dataController reloadLabStatusesWithBlock:nil];
[self.dataController clearHostInfoCache];
}
}

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42 changes: 39 additions & 3 deletions CAENLabStatus/DZCDataController.h
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Original file line number Diff line number Diff line change
Expand Up @@ -13,12 +13,48 @@ typedef enum {

@interface DZCDataController : NSObject

- (void)reloadLabStatusesWithBlock:(void(^)(NSError *error))block;

/**
* Gets each known lab and its status, loading data from the network into
* the cache if necessary.
*
* Calls your block with a dictionary with key `DZCLab`, object `NSNumber`
* with `int DZCLabStatus`.
*
* The `error` paramater to the block is nil if there was no error.
*/
- (void)labsAndStatusesWithBlock:(void(^)(NSDictionary *labs, NSError *error))block;

/**
* Gets statistics about computer usage in the given lab, loading data
* from the network into the cache if necessary.
*
* Calls your block with the statistics once any network activity is complete.
* `error` will be nil if these was no error.
*/
- (void)machineCountsInLab:(DZCLab *)lab withBlock:(void(^)(NSNumber *used, NSNumber *total, DZCLab *lab, NSError *error))block;

- (void)clearHostInfoCache;
/**
* Make the data controller (re)load and cache all lab statuses.
*
* This is intended to be used when the app launches or returns to
* foreground to ensure we show current data.
*
* Your block is called when the lab statuses are ready. `error`
* is nil if there was no error.
*/
- (void)reloadLabStatusesWithBlock:(void(^)(NSError *error))block;

/**
* Make the data controller (re)load and cache host info for the given lab.
*
* Your block is called when the host info is ready. `error`
* is nil if there was no error.
*/
- (void)reloadHostInfoForLab:(DZCLab *)lab withBlock:(void(^)(NSError *error))block;

/**
* Clears the cache. This affects lab status and host info.
*/
- (void)clearCache;

@end
223 changes: 127 additions & 96 deletions CAENLabStatus/DZCDataController.m
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Original file line number Diff line number Diff line change
Expand Up @@ -17,14 +17,25 @@
}
}

/* Number of times to retry failed API queries */
#define RETRIES ((NSUInteger)4)


@interface DZCDataController ()

@property (nonatomic, readonly, strong) DZCLabStatusApiClient *labStatusApiClient;
@property (nonatomic, readonly, strong) DZCHostInfoApiClient *hostInfoApiClient;
@property (nonatomic, readonly, strong) NSArray *labs;
@property (nonatomic, strong) id labStatuses;
@property (nonatomic, readonly, strong) NSSet *labs;

/* labStatuses is a dictionary that maps a lab object to an NSNumber with int DZCLabStatus.
* It can be set to nil to clear the cache; it is recreated as an empty mutable dictionary on any access. */
@property (nonatomic, strong) NSMutableDictionary *labStatuses;

/* labHostInfo is a dictionary that maps a lab object to an array of hosts in the lab.
* It can be set to nil to clear the cache; it is recreated as an empty mutable dictionary on any access/ */
@property (nonatomic, strong) NSMutableDictionary *labHostInfo;

- (void)setLabsFromApiResponse:(id)response;
- (NSString *)apiIdForLab:(DZCLab *)lab;

@end
Expand All @@ -33,90 +44,36 @@ @implementation DZCDataController

@synthesize labHostInfo = _labHostInfo, labs = _labs, labStatusApiClient = _labStatusApiClient, hostInfoApiClient = _hostInfoApiClient, labStatuses = _labStatuses;

// TODO refactor this implementation to achieve better logic/caching and API/network separation

/**
* Make the data controller (re)load all lab statuses.
*
* This is intended to be used when the app launches or returns to
* foreground to ensure we show current data.
*
* Your block is called when the response finishes, whether or
* not there is an error.
*/
- (void)reloadLabStatusesWithBlock:(void(^)(NSError *error))block
{
NSLog(@"Kicking off lab status request...");
[self.labStatusApiClient
getPath:@"lab-statuses.php"
parameters:nil
success:^(AFHTTPRequestOperation *operation, id responseObject) {
if (responseObject != nil) {
self.labStatuses = responseObject;
if (block) block(nil);
} else {
if (block) block([[NSError alloc] init]);
}
}
failure:^(AFHTTPRequestOperation *operation, NSError *error) {
if (block) block(error);
}
];
}

/**
* Gets each known lab and its status.
*
* Returns a dictionary with key DZCLab, object DZCLabStatus.
*/
- (void)labsAndStatusesWithBlock:(void(^)(NSDictionary *labs, NSError *error))block
{
void (^labsReady)(void) = ^ {
NSMutableDictionary *labsResult = [NSMutableDictionary dictionary];
void (^labsReady)(NSDictionary*) = ^(NSDictionary* labStatuses) {
if (block) block(labStatuses, nil);
};

if ([self.labStatuses count] != 0) {
labsReady(self.labStatuses);
} else {
__block NSUInteger retries = RETRIES;

for (id lab in self.labs) {
NSString* statusString = [self.labStatuses objectForKey:[self apiIdForLab:lab]];
DZCLabStatus status;

if ([statusString isEqualToString:DZCLabStatusStrings[DZCLabStatusOpen]]) {
status = DZCLabStatusOpen;
} else if ([statusString isEqualToString:DZCLabStatusStrings[DZCLabStatusReserved]]) {
status = DZCLabStatusReserved;
} else if ([statusString isEqualToString:DZCLabStatusStrings[DZCLabStatusReservedSoon]]) {
status = DZCLabStatusReservedSoon;
} else if ([statusString isEqualToString:DZCLabStatusStrings[DZCLabStatusPartiallyReserved]]) {
status = DZCLabStatusPartiallyReserved;
__block void (^reloadLabStatusResultBlock)(NSError *) = [^(NSError* error) {
if (error && retries > 0) {
NSLog(@"Retrying lab status query...");
retries--;
[self reloadLabStatusesWithBlock:reloadLabStatusResultBlock];
} else if (error) {
if (block) block(nil, error);
} else {
// nil, empty, or unrecognized string means the lab is either closed or not present but open
// defer to another, date/time processing controller
NSLog(@"Unknown status string '%@' for lab '%@' in building '%@'", statusString, [lab humanName], [lab building]);
status = [[DZCLabStatusHelper statusGuessForLab:(DZCLab *)lab] intValue];
labsReady(self.labStatuses);
}

[labsResult setObject:[NSNumber numberWithInt:status] forKey:lab];
}
} copy];

if (block) block(labsResult, nil);
};

if (self.labStatuses) {
labsReady();
} else {
[self reloadLabStatusesWithBlock:^(NSError *error) {
if (error) assert(0); // TODO handle error
labsReady();
}];
[self reloadLabStatusesWithBlock:reloadLabStatusResultBlock];
}
}

- (void)machineCountsInLab:(DZCLab *)lab withBlock:(void(^)(NSNumber *used, NSNumber *total, DZCLab *lab, NSError *error))block
{
void (^hostInfoReady)(void) = ^ {
// NOTE: the total count will differ from http://labwatch.engin.umich.edu/labs/mobile.php because that
// page hard codes the total host count in each lab.
// ... yep.

NSArray *hosts = [self.labHostInfo objectForKey:lab];
void (^hostInfoReady)(NSArray *) = ^(NSArray *hosts) {
NSUInteger used = 0;

for (id host in hosts) {
Expand All @@ -130,31 +87,70 @@ - (void)machineCountsInLab:(DZCLab *)lab withBlock:(void(^)(NSNumber *used, NSNu
};

if ([self.labHostInfo objectForKey:lab]) {
hostInfoReady();
hostInfoReady([self.labHostInfo objectForKey:lab]);
} else {
NSLog(@"Kicking off host info request for %@...", [self apiIdForLab:lab]);
__block NSUInteger retries = RETRIES;

[self.hostInfoApiClient
getPath:@"computers.json"
parameters:[NSDictionary dictionaryWithObjectsAndKeys:lab.building, @"building", lab.room, @"room", nil]
success:^(AFHTTPRequestOperation *operation, id responseObject) {
if (responseObject != nil) {
[self.labHostInfo setObject:responseObject forKey:lab];
hostInfoReady();
} else {
if (block) block(nil, nil, nil, [[NSError alloc] init]);
}
}
failure:^(AFHTTPRequestOperation *operation, NSError *error) {
if (block) block(nil, nil, nil, error);
}
];
__block void (^reloadHostInfoResultBlock)(NSError *) = [^(NSError* error) {
if (error && retries > 0) {
NSLog(@"Retrying host info query...");
retries--;
[self reloadHostInfoForLab:lab withBlock:reloadHostInfoResultBlock];
} else if (error) {
if (block) block(nil, nil, lab, error);
} else {
hostInfoReady([self.labHostInfo objectForKey:lab]);
}
} copy];

[self reloadHostInfoForLab:lab withBlock:reloadHostInfoResultBlock];
}
}

- (void)clearHostInfoCache
- (void)reloadLabStatusesWithBlock:(void(^)(NSError *error))block
{
NSLog(@"Kicking off lab status request...");

[self.labStatusApiClient getPath:@"lab-statuses.php"
parameters:nil
success:^(AFHTTPRequestOperation *operation, id responseObject) {
if (responseObject != nil) {
[self setLabsFromApiResponse:responseObject];
if (block) block(nil);
} else {
if (block) block([[NSError alloc] init]);
}
}
failure:^(AFHTTPRequestOperation *operation, NSError *error) {
if (block) block(error);
}
];
}

- (void)reloadHostInfoForLab:(DZCLab *)lab withBlock:(void(^)(NSError *error))block
{
NSLog(@"Kicking off host info request for %@...", [self apiIdForLab:lab]);

[self.hostInfoApiClient getPath:@"computers.json"
parameters:[NSDictionary dictionaryWithObjectsAndKeys:lab.building, @"building", lab.room, @"room", nil]
success:^(AFHTTPRequestOperation *operation, id responseObject) {
if (responseObject != nil) {
[self.labHostInfo setObject:responseObject forKey:lab];
if (block) block(nil);
} else {
if (block) block([[NSError alloc] init]);
}
}
failure:^(AFHTTPRequestOperation *operation, NSError *error) {
if (block) block(error);
}
];
}

- (void)clearCache
{
self.labHostInfo = nil;
self.labStatuses = nil;
}

#pragma mark - Private helper methods
Expand All @@ -164,6 +160,33 @@ - (NSString *)apiIdForLab:(DZCLab *)lab
return [NSString stringWithFormat:@"%@%@", lab.building, lab.room];
}

- (void)setLabsFromApiResponse:(id)response
{
self.labStatuses = nil;

for (id lab in self.labs) {
NSString* statusString = [response objectForKey:[self apiIdForLab:lab]];
DZCLabStatus status;

if ([statusString isEqualToString:DZCLabStatusStrings[DZCLabStatusOpen]]) {
status = DZCLabStatusOpen;
} else if ([statusString isEqualToString:DZCLabStatusStrings[DZCLabStatusReserved]]) {
status = DZCLabStatusReserved;
} else if ([statusString isEqualToString:DZCLabStatusStrings[DZCLabStatusReservedSoon]]) {
status = DZCLabStatusReservedSoon;
} else if ([statusString isEqualToString:DZCLabStatusStrings[DZCLabStatusPartiallyReserved]]) {
status = DZCLabStatusPartiallyReserved;
} else {
// nil, empty, or unrecognized string means the lab is either closed or not present but open
// defer to another, date/time processing controller
NSLog(@"fyi: unknown status string '%@' for lab '%@' in building '%@'", statusString, [lab humanName], [lab building]);
status = [[DZCLabStatusHelper statusGuessForLab:(DZCLab *)lab] intValue];
}

[self.labStatuses setObject:[NSNumber numberWithInt:status] forKey:lab];
}
}

#pragma mark - Property Overrides

- (DZCLabStatusApiClient *)labStatusApiClient {
Expand All @@ -188,15 +211,23 @@ - (NSMutableDictionary *)labHostInfo
return _labHostInfo;
}

- (NSArray *)labs
- (NSMutableDictionary *)labStatuses
{
if (!_labStatuses) {
_labStatuses = [NSMutableDictionary dictionary];
}
return _labStatuses;
}

- (NSSet *)labs
{
// I have to do this because the way the API is designed requires prior knowledge of all the labs
// for various reasons: to determine whether one is closed, to weed out duplicates (!), etc.
// for various reasons: to determine whether one is closed, weed out duplicates (!), get accurate counts, etc.

// based on view-source:http://labwatch.engin.umich.edu/labs/mobile.php

if (!_labs) {
_labs = [NSArray arrayWithObjects:
_labs = [NSSet setWithObjects:
[[DZCLab alloc] initWithBuilding:@"PIERPONT" room:@"B505" humanName:@"Pierpont B505"],
[[DZCLab alloc] initWithBuilding:@"PIERPONT" room:@"B507" humanName:@"Pierpont B507"],
[[DZCLab alloc] initWithBuilding:@"PIERPONT" room:@"B521" humanName:@"Pierpont B521"],
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2 changes: 1 addition & 1 deletion CAENLabStatus/DZCLabsViewController.h
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,6 @@

@interface DZCLabsViewController : UITableViewController

@property(nonatomic, weak) DZCDataController *dataController;
@property(nonatomic, strong) DZCDataController *dataController;

@end
17 changes: 13 additions & 4 deletions CAENLabStatus/DZCLabsViewController.m
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Original file line number Diff line number Diff line change
Expand Up @@ -183,15 +183,24 @@ - (NSString *)tableView:(UITableView *)tableView titleForHeaderInSection:(NSInte
- (void)refreshData
{
self.labs = nil;
[self.dataController clearHostInfoCache];
[self.dataController reloadLabStatusesWithBlock:^(NSError *error) {
[self loadData];
}];
[self.dataController clearCache];
[self loadData];
}

- (void)loadData
{
[self.dataController labsAndStatusesWithBlock:^(NSDictionary *labs, NSError *error) {

if (error) {
UIAlertView *alert = [[UIAlertView alloc] initWithTitle:NSLocalizedString(@"Error Retrieving Data", nil)
message:NSLocalizedString(@"Please ensure you have a network connection. If you do, the CAEN lab info service might be down.\n\nShake the device to try refreshing the app.", nil)
delegate:nil
cancelButtonTitle:NSLocalizedString(@"OK", nil)
otherButtonTitles:nil];
[alert show];
return;
}

// map statuses to sections for display
// TODO this mapping can be made cleaner

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