How to reference and modify a std::unique_ptr's underlying value in another function?

.everyoneloves__top-leaderboard:empty,.everyoneloves__mid-leaderboard:empty,.everyoneloves__bot-mid-leaderboard:empty{ height:90px;width:728px;box-sizing:border-box;
}

-2

I am trying to modify the value within a unique_ptr, but inside another function which doesn't actually own the unique_ptr, as follows:

void my_func(Foo* foo) {

  foo->set_bar("a");

} 



int main() {

  auto foo = std::MakeUnique<Foo>();



  my_func(foo.get());



  cout << foo->bar;

}

I thought this would work, except I'm met with an error complaining of a deleted constructor. Is there a way to make this pattern work?

asked Nov 29 '18 at 1:29

bonnoz05

what is a MakeUnique? What is a Foo? Please post a Minimal, Complete, and Verifiable example

– xaxxon
Nov 29 '18 at 1:33

Inside? That's a pointer. Managed by? That's what the pointer refers to.

– Deduplicator
Nov 29 '18 at 1:41

Once I make the required corrections and fill in the blanks I'm not seeing any problems: ideone.com/zZwgZv . Minimal, Complete, and Verifiable example definitely required.

– user4581301
Nov 29 '18 at 1:45

Unrelated suggestion: If you make my_func look more like void my_func(const std::unique_ptr<Foo> & foo), the ownership of foo remains clear. Last thing you want is some knucklehead coming along and dropping a delete foo; somewhere in there.

– user4581301
Nov 29 '18 at 1:51

add a comment |

-2

I am trying to modify the value within a unique_ptr, but inside another function which doesn't actually own the unique_ptr, as follows:

void my_func(Foo* foo) {

  foo->set_bar("a");

} 



int main() {

  auto foo = std::MakeUnique<Foo>();



  my_func(foo.get());



  cout << foo->bar;

}

I thought this would work, except I'm met with an error complaining of a deleted constructor. Is there a way to make this pattern work?

asked Nov 29 '18 at 1:29

bonnoz05

what is a MakeUnique? What is a Foo? Please post a Minimal, Complete, and Verifiable example

– xaxxon
Nov 29 '18 at 1:33

Inside? That's a pointer. Managed by? That's what the pointer refers to.

– Deduplicator
Nov 29 '18 at 1:41

Once I make the required corrections and fill in the blanks I'm not seeing any problems: ideone.com/zZwgZv . Minimal, Complete, and Verifiable example definitely required.

– user4581301
Nov 29 '18 at 1:45

Unrelated suggestion: If you make my_func look more like void my_func(const std::unique_ptr<Foo> & foo), the ownership of foo remains clear. Last thing you want is some knucklehead coming along and dropping a delete foo; somewhere in there.

– user4581301
Nov 29 '18 at 1:51

add a comment |

-2

I am trying to modify the value within a unique_ptr, but inside another function which doesn't actually own the unique_ptr, as follows:

void my_func(Foo* foo) {

  foo->set_bar("a");

} 



int main() {

  auto foo = std::MakeUnique<Foo>();



  my_func(foo.get());



  cout << foo->bar;

}

I thought this would work, except I'm met with an error complaining of a deleted constructor. Is there a way to make this pattern work?

asked Nov 29 '18 at 1:29

bonnoz05

I am trying to modify the value within a unique_ptr, but inside another function which doesn't actually own the unique_ptr, as follows:

void my_func(Foo* foo) {

  foo->set_bar("a");

} 



int main() {

  auto foo = std::MakeUnique<Foo>();



  my_func(foo.get());



  cout << foo->bar;

}

I thought this would work, except I'm met with an error complaining of a deleted constructor. Is there a way to make this pattern work?

c++ unique-ptr

asked Nov 29 '18 at 1:29

bonnoz05

asked Nov 29 '18 at 1:29

bonnoz05

asked Nov 29 '18 at 1:29

bonnoz05

asked Nov 29 '18 at 1:29

bonnoz05

asked Nov 29 '18 at 1:29

bonnoz05

what is a MakeUnique? What is a Foo? Please post a Minimal, Complete, and Verifiable example

– xaxxon
Nov 29 '18 at 1:33

Inside? That's a pointer. Managed by? That's what the pointer refers to.

– Deduplicator
Nov 29 '18 at 1:41

Once I make the required corrections and fill in the blanks I'm not seeing any problems: ideone.com/zZwgZv . Minimal, Complete, and Verifiable example definitely required.

– user4581301
Nov 29 '18 at 1:45

Unrelated suggestion: If you make my_func look more like void my_func(const std::unique_ptr<Foo> & foo), the ownership of foo remains clear. Last thing you want is some knucklehead coming along and dropping a delete foo; somewhere in there.

– user4581301
Nov 29 '18 at 1:51

add a comment |

what is a MakeUnique? What is a Foo? Please post a Minimal, Complete, and Verifiable example

– xaxxon
Nov 29 '18 at 1:33

Inside? That's a pointer. Managed by? That's what the pointer refers to.

– Deduplicator
Nov 29 '18 at 1:41

Once I make the required corrections and fill in the blanks I'm not seeing any problems: ideone.com/zZwgZv . Minimal, Complete, and Verifiable example definitely required.

– user4581301
Nov 29 '18 at 1:45

Unrelated suggestion: If you make my_func look more like void my_func(const std::unique_ptr<Foo> & foo), the ownership of foo remains clear. Last thing you want is some knucklehead coming along and dropping a delete foo; somewhere in there.

– user4581301
Nov 29 '18 at 1:51

what is a MakeUnique? What is a Foo? Please post a Minimal, Complete, and Verifiable example

– xaxxon
Nov 29 '18 at 1:33

Inside? That's a pointer. Managed by? That's what the pointer refers to.

– Deduplicator
Nov 29 '18 at 1:41

Once I make the required corrections and fill in the blanks I'm not seeing any problems: ideone.com/zZwgZv . Minimal, Complete, and Verifiable example definitely required.

– user4581301
Nov 29 '18 at 1:45

Unrelated suggestion: If you make my_func look more like void my_func(const std::unique_ptr<Foo> & foo), the ownership of foo remains clear. Last thing you want is some knucklehead coming along and dropping a delete foo; somewhere in there.

– user4581301
Nov 29 '18 at 1:51

add a comment |

1 Answer
1

active

oldest

votes

I will assume you are actually using std::make_unique<Foo>().

Since it is an error with construction, this is most likely a problem with the Foo type, not with what you are trying to do with it. Although, it could also stem from the set_bar() function.

Using std::make_unique<Foo>() will attempt to use the default constructor (the one with no arguments). It would appear that your Foo type does not have a default constructor. Although, without the implementation of Foo at hand, this is just a guess. You need to give std::make_unique<Foo>() arguments that correspond to one of the defined constructors of Foo ¹.

Re: What you are trying to do - this seems like it should work. Although, since it is taking a raw pointer, you should consider doing some nullptr checks.

^{1: If there is at least one constructor defined, where one is not the default constructor, the default constructor is deleted.}

edited Nov 29 '18 at 2:01

Remy Lebeau

342k19267461

answered Nov 29 '18 at 1:53

Bar Stool

1735

add a comment |

Your Answer

StackExchange.ifUsing("editor", function () {
StackExchange.using("externalEditor", function () {
StackExchange.using("snippets", function () {
StackExchange.snippets.init();
});
});
}, "code-snippets");

StackExchange.ready(function() {
var channelOptions = {
tags: "".split(" "),
id: "1"
};
initTagRenderer("".split(" "), "".split(" "), channelOptions);

StackExchange.using("externalEditor", function() {
// Have to fire editor after snippets, if snippets enabled
if (StackExchange.settings.snippets.snippetsEnabled) {
StackExchange.using("snippets", function() {
createEditor();
});
}
else {
createEditor();
}
});

function createEditor() {
StackExchange.prepareEditor({
heartbeatType: 'answer',
autoActivateHeartbeat: false,
convertImagesToLinks: true,
noModals: true,
showLowRepImageUploadWarning: true,
reputationToPostImages: 10,
bindNavPrevention: true,
postfix: "",
imageUploader: {
brandingHtml: "Powered by u003ca class="icon-imgur-white" href="https://imgur.com/"u003eu003c/au003e",
contentPolicyHtml: "User contributions licensed under u003ca href="https://creativecommons.org/licenses/by-sa/3.0/"u003ecc by-sa 3.0 with attribution requiredu003c/au003e u003ca href="https://stackoverflow.com/legal/content-policy"u003e(content policy)u003c/au003e",
allowUrls: true
},
onDemand: true,
discardSelector: ".discard-answer"
,immediatelyShowMarkdownHelp:true
});

}
});

draft saved

draft discarded

Sign up or log in

StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});

Post as a guest

Name

Required, but never shown

StackExchange.ready(
function () {
StackExchange.openid.initPostLogin('.new-post-login', 'https%3a%2f%2fstackoverflow.com%2fquestions%2f53530571%2fhow-to-reference-and-modify-a-stdunique-ptrs-underlying-value-in-another-func%23new-answer', 'question_page');
}
);

Post as a guest

Name

Required, but never shown

1 Answer
1

active

oldest

votes

1 Answer
1

active

oldest

votes

I will assume you are actually using std::make_unique<Foo>().

Since it is an error with construction, this is most likely a problem with the Foo type, not with what you are trying to do with it. Although, it could also stem from the set_bar() function.

Re: What you are trying to do - this seems like it should work. Although, since it is taking a raw pointer, you should consider doing some nullptr checks.

^{1: If there is at least one constructor defined, where one is not the default constructor, the default constructor is deleted.}

edited Nov 29 '18 at 2:01

Remy Lebeau

342k19267461

answered Nov 29 '18 at 1:53

Bar Stool

1735

add a comment |

I will assume you are actually using std::make_unique<Foo>().

Since it is an error with construction, this is most likely a problem with the Foo type, not with what you are trying to do with it. Although, it could also stem from the set_bar() function.

Re: What you are trying to do - this seems like it should work. Although, since it is taking a raw pointer, you should consider doing some nullptr checks.

^{1: If there is at least one constructor defined, where one is not the default constructor, the default constructor is deleted.}

edited Nov 29 '18 at 2:01

Remy Lebeau

342k19267461

answered Nov 29 '18 at 1:53

Bar Stool

1735

add a comment |

I will assume you are actually using std::make_unique<Foo>().

Since it is an error with construction, this is most likely a problem with the Foo type, not with what you are trying to do with it. Although, it could also stem from the set_bar() function.

Re: What you are trying to do - this seems like it should work. Although, since it is taking a raw pointer, you should consider doing some nullptr checks.

^{1: If there is at least one constructor defined, where one is not the default constructor, the default constructor is deleted.}

edited Nov 29 '18 at 2:01

Remy Lebeau

342k19267461

answered Nov 29 '18 at 1:53

Bar Stool

1735

I will assume you are actually using std::make_unique<Foo>().

Since it is an error with construction, this is most likely a problem with the Foo type, not with what you are trying to do with it. Although, it could also stem from the set_bar() function.

Re: What you are trying to do - this seems like it should work. Although, since it is taking a raw pointer, you should consider doing some nullptr checks.

^{1: If there is at least one constructor defined, where one is not the default constructor, the default constructor is deleted.}

edited Nov 29 '18 at 2:01

Remy Lebeau

342k19267461

answered Nov 29 '18 at 1:53

Bar Stool

1735

edited Nov 29 '18 at 2:01

Remy Lebeau

342k19267461

edited Nov 29 '18 at 2:01

Remy Lebeau

342k19267461

edited Nov 29 '18 at 2:01

Remy Lebeau

342k19267461

answered Nov 29 '18 at 1:53

Bar Stool

1735

answered Nov 29 '18 at 1:53

Bar Stool

1735

answered Nov 29 '18 at 1:53

Bar Stool

1735

add a comment |

draft saved

draft discarded

Thanks for contributing an answer to Stack Overflow!

Please be sure to answer the question. Provide details and share your research!

But avoid …

Asking for help, clarification, or responding to other answers.

Making statements based on opinion; back them up with references or personal experience.

To learn more, see our tips on writing great answers.

draft saved

draft discarded

Sign up or log in

StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});

Post as a guest

Name

Required, but never shown

Post as a guest

Name

Required, but never shown

Sign up or log in

StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});

Post as a guest

Name

Required, but never shown

Sign up or log in

StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});

Post as a guest

Name

Required, but never shown

Sign up or log in

StackExchange.ready(function () {
StackExchange.helpers.onClickDraftSave('#login-link');
});

Post as a guest

Name

Required, but never shown

Name

Required, but never shown

Name

Required, but never shown

This page is only for reference, If you need detailed information, please check here

搜尋此網誌

Btukfyl