IOS stage learning 22nd-day notes (JSON data format Introduction), 22nd-day json

IOS stage learning 22nd-day notes (JSON data format Introduction), 22nd-day json

Knowledge points of IOS Learning (oc language)

I. JSON Data Format

1) concept: json is A network data transmission format with A value/object: {"A": 1, "B": "2 "...} Dictionary; Object Sequence: [,] Two Data Types

 

2) URLWithString encapsulates the string URL into an NSURL object, for example:

1 NSString *urlStr=@"http://10.0.8.8/sns/my/user_list.php?number=202 &page=";//get  post3 NSURL *url=[NSURL URLWithString:urlStr];

3) fileURLWithPath encapsulates the local file address into an NSURL object, for example:

1 url=[NSURL fileURLWithPath:@“Users/kingkong/JsonFile/test.json”];

 

4) initWithContentsOfURL is used to synchronize json data on the request network, for example:

1 NSData *json=[[NSData alloc]initWithContentsOfURL:url];

5) initWithData parses JSON data into a string, for example:

1 NSString *strjson=[[NSString alloc]initWithData:json encoding:NSUTF8StringEncoding];2 NSLog(@"%@",strjson);

 

6) options: NSJSONReadingAllowFragments can directly parse json data into dictionary objects, for example:

1 // read the file content (json data) 2 NSData * jsonData = [[NSData alloc] initWithContentsOfFile: path]; 3 // parse json data directly to the dictionary object 4 NSDictionary * dict1 = [NSJSONSerialization JSONObjectWithData: jsonData options: 5 NSJSONReadingAllowFragments error: nil];

 

7) obtain the network image data and save it to a local (similar to download) instance code

1 // obtain resources (image data) on the server 2 NSData * iconData = [NSData dataWithContentsOfURL: [NSURL URLWithString: iconUrl]; 3 NSString * iconFile = [fullPath stringByAppendingPathComponent: @ "icon.png"]; 4 // write image data to a file (Save the image to the file) 5 [iconData writeToFile: iconFile atomically: YES];

 

8) Obtain JSON data and traverse the data instance code:

1 // request network path 2 NSString * path = @ "http: // 10.0.8.8/sns/my/user_list.php? Number = 20 & page = "; 3 // construct URL 4 NSURL * url = [NSURL URLWithString: path]; 5 // request to obtain JSON data 6 NSData * json = [[NSData alloc] initWithContentsOfURL: url]; 7 // parse JSON data into object 8 id obj = [NSJSONSerialization JSONObjectWithData: json options: NSJSONReadingMutableContainers error: nil]; 9 // traverse JSON data 10 if ([obj isKindOfClass: [NSDictionary class]) {11 NSDictionary * dict = (NSDictionary *) obj; 12 NSArray * array = [dict objectForKey: @ "users"]; 13 for (NSDictionary * dic in array) {14 NSLog (@ "username: % @ \ tuid: % @ ", [dic objectForKey: @" username "], [dic objectForKey: @" uid "]); 15} 16}

9) encode the dictionary set into JSON data instance code

1 // construct Dictionary data 2 NSArray * arry = @ [@ "pass1234", @ "123456"]; 3 NSDictionary * dic = [[NSDictionary alloc] initWithObjectsAndKeys: @ "KingKong", @ "username", @ "male", @ "sex", arry, @ "password", nil]; 4 // convert dictionary set data to JSON data type 5 NSData * json = [NSJSONSerialization dataWithJSONObject: dic options: NSJSONWritingPrettyPrinted error: nil]; 6 // reparse JSON data 7 NSString * strjson = [[NSString alloc] initWithData: json encoding: NSUTF8StringEncoding]; 8 NSLog (@ "% @", strjson );

10) JSON parsing tool Jason. app [Download]

11) Date function operations in NSDate OC [Details]