Learn the Swift from the Start learning Note (Day--cocoa) error handling mode

original articles, welcome reprint. Reprint Please specify: Dongsheng's blog

Swifterror handling mode, inswift1.xand theSwift 2.0are two different modes.

Swift 1.xCode error handling mode usesCocoaFrame error Handling mode, up to nowobjective-cThis processing mode is also used, andSwift2.0then adopted theDo-try-catcherror handling mode.

The following example code reads a string from a file into memory if you use the Swift 1.x The error handling mode code is as follows:

Import Foundation var err:nserror?        Define optional nserror? variable let contents = NSString (Contentsoffile:filepath,             êencoding:nsutf8stringencoding, Error: & ERR) If err! = Nil {      //To determine if the ERR variable is still nil    //error handling}

nserror? must be an optional variable, because you want to initialize it to a Nil .

JudgingErrwhether the variable is stillNil, if it is stillNilin the Code

Let contents = NSString (Contentsoffile:filepath,                     êencoding:nsutf8stringencoding, error: &err)

No error occurred during method call, otherwise an error occurred.

The constructor for the above code, its Swift syntax is defined as follows:

Init? (Contentsofurl url:nsurl,         encoding enc:uint,            error Error:nserrorpointer)

the last parameter of the constructor isNserrorpointer(i.e.Nserrorpointer), then in the actual call we need to passErrvariable address (that is,&err),&is a fetch address character. When the method call is complete, if there is an errorErrThe variable is assigned a value.

Welcome to follow Dongsheng Sina Weibo@tony_Dongsheng.
Learn about the latest technical articles, books, tutorials and information on the public platform of the smart Jie classroom
?
More ProductsIOS,Cocos, mobile Design course please pay attention to the official website of Chi Jie Classroom:http://www.zhijieketang.com
Smart-Jie Classroom Forum Website:http://51work6.com/forum.php

Learn the Swift from the Start learning Note (Day--cocoa) error handling mode