无法返回String值并将其附加...为什么？

Question

I am writing an app and am having problems returning a simple string value, and I'm not sure why. 我正在编写一个应用程序，但是在返回简单的字符串值时遇到问题，我不确定为什么。

The function I am using (within a file called APIManager.m) is: 我正在使用的功能（在名为APIManager.m的文件中）是：

- (NSString*) returnVenueUrl {
NSString *venueUrl = [devEnvironment stringByAppendingString:@"venue/id/"];
return venueUrl;

} }

I can return this properly by doing this in another .m file: 我可以通过在另一个.m文件中执行此操作来正确返回它：

APIManager *apiManager = [APIManager apiManager];
NSLog(@"view venue URL is here: %@", [apiManager returnVenueUrl]);

But when I go to append a variable cast as a String onto it, I get nothing.. 但是，当我将变量转换为String附加到变量上时，我什么也没得到。

venueURL = [apiManager returnVenueUrl];
venueURL = [venueURL stringByAppendingString:venueId];

NSLog(@"the Full Venue URL is: %", venueURL);

If anyone has any advice on how to fix this, it would be much appreciated! 如果有人对如何解决此问题有任何建议，将不胜感激！

Answer 1

使用NSMutableString NSString是不可变的（aka不可修改）